Note: Descriptions are shown in the official language in which they were submitted.
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
PHOTONIC CRYSTAL FIBERS AND
MEDICAL SYSTEMS INCLUDING PHOTONIC CRYSTAL
FIBERS
CROSS-REFERENCE TO RELATED APPLICATIONS
Under 35 USC ~119(e)(1), this application claims the benefit of Provisional
Patent Application 60/560,458, entitled "PHOTONIC CRYSTAL FIBER
APPLICATIONS," filed on April 8, 2004, Provisional Patent Application
60/561,020,
s entitled "PHOTONIC CRYSTAL FIBER APPLICATIONS," filed on April 9, 2004,
Provisional Patent Application 60/584,098, entitled "PHOTONIC CRYSTAL FIBER
APPLICATIONS," filed on June 30, 2004, Provisional Patent Application
60/628,462, entitled "PHOTONIC CRYSTAL FIBER APPLICATIONS," filed on
November 16, 2004, Provisional Patent Application 60/640,536, entitled
~ o "OMNIGUIDE PHOTONIC BANDGAP FIBERS FOR FLEXIBLE DELIVERY OF
COZ LASERS IN LARYNGOLOGY," filed on December 30, 2004, and Provisional
Patent Application 60/658,531, entitled "PHOTONIC CRYSTAL FIBERS," filed on
March 4, 2005. The contents of all the above-listed provisional patent
applications
are hereby incorporated by reference in their entirety.
15 BA CI~GROUND
Lasers are prevalent in many areas of medicine today. For example, lasers
find application in diverse medical areas, such as surgery, veterinary
medicine,
dentistry, ophthalmology, and in aesthetic medical procedures.
In many of these applications, an optical fiber is used to deliver radiation
from
2o a laser to the target region of the patient. Conventional optical fibers
are excellent
waveguides for radiation having wavelengths in the visible or near-infrared
portion of
the electromagnetic spectrum (e.g., wavelengths of about 2 microns or less).
However, conventional optical fibers are, in general, not suitable in
applications
where high power laser radiation with relatively long wavelengths is used.
25 Accordingly, many medical laser systems that deliver high power (e.g.,
about 10
Watts or more), long wavelength (e.g., greater than about 2 microns), do so
using an
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
articulated arm that includes optical components that guide the laser
radiation through
rigid conduits or free space from the laser to the target.
SUMMARY
Photonic crystal fibers can be used in medical laser systems to guide
radiation
from a radiation source (e.g., a laser) to a target location of a patient. In
general,
photonic crystal fibers include a region surrounding a core that provides
extremely
effective confinement of certain radiation wavelengths to the core. These so-
called
confinement regions can be formed exclusively from amorphous dielectric
materials
(e.g., glasses and/or polymers), and can provide effective confinement while
still
1 o being relatively thin. Accordingly, photonic crystal fibers can include
thin, flexible
fiber's capable of guiding extremely high power radiation.
Moreover, photonic crystal fibers can be drawn from a preform, resulting in ,
fibers that are relatively inexpensive to produce compared to other waveguides
that
are not drawn. Fiber manufacturing techniques also provides substantial
production
capacity, e.g., thousands of meters of fiber can be drawn from a single
preform. The
conversion in the draw process from a relatively short preform to very long
lengths of
fiber can effectively smooth out any perturbations from the desired structure
that exist
in the preform, producing low-loss, low-defect fiber.
In general, in a first aspect, the invention features systems, including a
2o photonic crystal fiber including a core extending along a waveguide axis
and a
dielectric confinement region surrounding the core, the dielectric confinement
region
being configured to guide radiation along the waveguide axis from an input end
to an
output end of the photonic crystal fiber. The systems also includes a
handpiece
attached to the photonic crystal fiber, wherein the handpiece allows an
operator to
control the orientation of the output end to direct the radiation to a target
location of a
patient.
Embodiments of the systems can include one or more of the following features
and/or aspects of other aspects.
The handpiece can include an endoscope. The endoscope can include a
so flexible conduit and a portion of the photonic crystal fiber is threaded
through a
channel in the flexible conduit. The endoscope can include an actuator
mechanically
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
coupled to the flexible conduit configured to bend a portion of the flexible
conduit
thereby allowing the operator to vary the orientation of the output end. The
actuator
can be configured to bend the portion of the flexible conduit so that the bent
portion
of the flexible conduit has a radius of curvature of about 12 centimeters or
less (e.g.,
s about 10 centimeters or less, about 8 centimeters or less, about 5
centimeters or less,
about 3 centimeters or less). The actuator can be configured to bend the
flexible
conduit within a bend plane. The handpiece can be attached to the photonic
crystal
fiber to maintain an orientation of the dielectric confinement region to
control the
orientation of the photonic crystal fiber about its waveguide axis within the
flexible
o conduit. The attachment between the handpiece and the photonic crystal fiber
can
prevent twisting of the fiber by more than about 10 degrees (e.g., by more
than about
degrees) while maintaining operation. The endoscope can further include an
auxiliary conduit including a first portion coupled to the flexible conduit,
wherein the
photonic crystal fiber is threaded through a channel in the auxiliary conduit
into the
channel of the flexible conduit, the auxiliary conduit further comprising a
second
portion moveable with respect to the first portion, wherein the photonic
crystal fiber is
attached to the second portion and moving the second portion allows the
operator to
extend or retract the output end relative to an end of the flexible conduit.
The second
portion can extend or retract with respect to the first portion. The auxiliary
conduit
2o can be a rigid conduit.
In some embodiments, the handpiece includes a conduit and a portion of the
photonic crystal fiber is threaded through the conduit. The conduit can
include a bent
portion. The conduit can be formed from a deformable material. The handpiece
can
further include an actuator mechanically coupled to the conduit configured to
bend a
portion of the conduit thereby allowing the operator to vary the orientation
of the
output end.
The handpiece can include a tip extending past the output end that provides a
minimum standoff distance of about 1 millimeter or more between the output end
and
the target location.
so The photonic crystal fiber can be sufficiently flexible to guide the
radiation to
the target location while a portion of the photonic crystal fiber is bent
through an
angle of about 90 degrees or more and the portion has a radius of curvature of
about
3
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
12 centimeters or less. The radiation can have an average power at the output
end of
about 1 Watt or more while the portion of the photonic crystal fiber is bent
through an
angle of about 90 degrees or more and the portion has a radius of curvature of
about
12 centimeters or less. The radiation can have an average power at the output
end of
about 5 Watts or more while the portion of the photonic crystal fiber is bent
through
an angle of about 90 degrees or more and the portion has a radius of curvature
of
about 12 centimeters or less. The photonic crystal fiber can be sufficiently
flexible to
guide the radiation to the target location while the portion of the photonic
crystal fiber
is bent through an angle of about 90 degrees or more and the portion has a
radius of
io curvature of about 10 centimeters or less (e.g., about 5 centimeters or
less).
The dielectric confinement region can include a layer of a first dielectric
material arranged in a spiral around the waveguide axis. The dielectric
confinement
region can further include a layer of a second dielectric material arranged in
a spiral
around the waveguide axis, the second dielectric material having a different
refractive
index from the first dielectric material. The first dielectric material can
be.a glass
(e.g., a chalcogenide glass). The second dielectric material can be a polymer.
The
dielectric confinement region can include at least one layer of a chalcogenide
glass.
The dielectric confinement region can include at least one layer of a
polymeric
material. In some embodiments, the dielectric confinement region includes at
least
one layer of a first dielectric material extending along the waveguide axis
and at least
one layer of a second dielectric material extending along the waveguide axis,
wherein
the first and second dielectric materials can be co-drawn with the first
dielectric
material.
The core can be a hollow core. The system can further include a fluid source
2s coupled to the input end or output end, wherein during operation the fluid
source
supplies a fluid through the core. The fluid can be a gas.
The core can have a diameter of about 1,000 microns or less (e.g., about 500
microns or less). The photonic crystal fiber can have an outer diameter of
about 2,000
microns or less at the output end.
so In some embodiments, the system further includes an optical waveguide and a
connector that attaches the optical waveguide to the photonic crystal fiber.
The
optical waveguide can be a second photonic crystal fiber. The system can also
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
include a conduit surrounding the optical waveguide. The conduit can be more
rigid
than the optical waveguide. The system can include a fluid source coupled to
the
conduit and wherein during operation the fluid source supplies a fluid to the
conduit.
The system can further include a laser to produce the radiation and direct it
towards the input end of the photonic crystal fiber. The laser can be a C02
laser. The
radiation can have a wavelength of about 2 microns or more. In some
embodiments,
the radiation has a wavelength of about 10.6 microns.
In certain embodiments, the system further includes an auxiliary radiation
source and at least one additional fiber mechanically coupled to the photonic
crystal
1 o fiber, the additional waveguide being configured to deliver auxiliary
radiation from
the auxiliary radiation source to the target location. The additional fiber
can be
mechanically coupled to the photonic crystal fiber by the handpiece. The
auxiliary
radiation source can be a second Iaser, different from the laser positioned to
direct the
radiation to the input end of the photonic crystal fiber. The second laser can
be an
Nd:YAG laser, a diode laser, or a pulsed dye laser. The auxiliary radiation
can have a
wavelength in the visible portion of the electromagnetic spectrum.
At least a portion of the photonic crystal can be sterilized.
In general, in another aspect, the invention features articles that include a
length of a photonic crystal fiber, the photonic crystal fiber including a
core extending
2o along a waveguide axis and a dielectric confinement region surrounding the
core, the
dielectric confinement region being configured to guide radiation along the
waveguide axis from an input end to an output end of the photonic crystal
fiber,
wherein the length of the photonic crystal fiber is sterilized.
The articles can further include a sealed package containing the length of the
2s photonic crystal fiber. Embodiments of the articles can include one or more
of the
features of other aspects.
In general, in a further aspect, the invention features methods that include
directing radiation into an input end of a photonic crystal fiber and using a
handpiece
attached to the photonic crystal fiber to control the orientation of an output
end of the
so photonic crystal fiber and direct radiation emitted from the output end
towards a
target location of a patient. Embodiments of the methods can include one or
more of
the features of other aspects.
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
In general, in another aspect, the invention features methods that include
directing radiation to a target location of a patient through a photonic
crystal fiber, the
photonic crystal fiber having a hollow core and flowing a fluid through the
hollow
core to the target location of the patient.
s Embodiments of the methods can include one or more of the following
features and/or features of other aspects.
The radiation can have sufficient power to incise, excise, or ablate tissue at
the
target location. The fluid can have a sufficient pressure and temperature to
coagulate
blood at the target location.
1 o The methods can include bending the photonic crystal fiber while directing
the
radiation and the fluid to the target location. Bending the fiber can include
bending a
portion of the fiber through about 45° or more to have a radius of
curvature of about
12 centimeters or less.
Directing the radiation and the fluid to the target location can include
holding
15 a portion of a handpiece attached to the photonic crystal fiber and
controlling the
orientation of the output end using the handpiece.
The fluid can be a gas, a liquid, or a superfluid. In embodiments where the
fluid is gas, the gas can have a pressure of about 0.5 PSI or more (e.g.,
about 1 PSI or
more) at the output end. The gas can have a temperature of about 50°C
or more (e.g.,
2o about 80°C or more) at the target location. The gas can be air. The
gas can include
carbon dioxide, oxygen, nitrogen, helium, neon, argon, krypton, or xenon. The
gas
can be a substantially pure gas. For example, the gas can include about 98% or
more
of a single component gas. Alternatively, in some embodiments, the gas is gas
mixture.
2s The fluid can be flowed into the hollow core at a rate of about 1 liter per
minute or more (e.g., about 2 liters per minute or more, about 5 liters per
minute or
more, about 8 liters per minute or more).
The radiation can have a wavelength of about 2 microns or more (e.g., about
10.6 microns). The radiation can have an average power of about 1 Watt or more
at
3o the target location.
In general, in a further aspect, the invention features apparatus that include
a
photonic crystal fiber including a core extending along a waveguide axis and a
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
dielectric confinement region surrounding the core, the dielectric confinement
region
being configured to guide radiation along the waveguide axis from an input end
to an
output end of the photonic crystal fiber, and a sleeve coupled to the output
end of the
photonic crystal fiber to allow the radiation to pass through the sleeve and
exit the
s sleeve through a primary opening, the sleeve further comprising one or more
secondary openings positioned so that gas flowed into the sleeve exits the
sleeve
through the secondary openings.
Embodiments of the apparatus can include one or more of the following
features and/or features of other aspects.
1 o The gas flowed into the sleeve can exit the sleeve through the primary
opening
in addition to through the secondary openings. The apparatus can further
include a
transparent element positioned between the primary opening and the secondary
openings that substantially transmits the radiation as it passes through the
sleeve. The
transparent element can substantially prevent gas from exiting the sleeve
through the
y5 primary opening. The transparent element can include ZnSe.
The apparatus can further include a conduit positioned relative to the
secondary opening so that gas exiting the sleeve through the secondary opening
is
drawn into an input end of the conduit.
The secondary opening can be positioned near to the primary opening. The
2o primary opening can have a diameter that is smaller than an outer diameter
of the
photonic crystal fiber at the output end. The apparatus can further include a
focusing
element attached to the sleeve to focus the radiation passing through the
sleeve.
Alternatively, or additionally, the can include a reflecting element attached
to the
sleeve to reflect the radiation passing through the sleeve.
25 In general, in another aspect, the invention features apparatus that
include an
assembly including a radiation input port configured to receive radiation from
a
radiation source and an output port configured to couple the radiation to a
photonic
crystal fiber, the assembly further including a retardation element positioned
to
modify a polarization state of the radiation received from the radiation
source before
3o it is coupled to the photonic crystal fiber.
Embodiments of the apparatus can include one or more of the following
features andlor features of other aspects.
7
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
The assembly can further include a gas input port configured to receive gas
from a gas source. The photonic crystal fiber can have a hollow core. The
output
port can be further configured to couple the gas received from the gas source
into the
hollow core of the photonic crystal fiber. The apparatus can include the gas
source.
The retardation element can be a reflective retardation element. The apparatus
can include the radiation source, wherein the radiation from the radiation
source
includes radiation having a wavelength ~,. The reflective retardation element
can
include a mirror and a retardation layer having an optical thickness of about
~, or less
disposed on a surface of the mirror. The retardation layer can have an optical
o thickness of about 7~/4 along a direction about 45° relative to a
normal to the surface
of the mirror. ~, can be about 2 microns or more. For example, ~, can be about
10.6
microns.
The retardation element can be a transmissive retardation element.
The retardation element can modify the polarization state of the radiation
from
i s a substantially linear polarization state to a substantially non-linear
polarization state.
The substantially non-linear polarization state can be a substantially
circular
polarization state.
The assembly can further include a focusing element configured to focus the
radiation entering the assembly at the radiation input port to a waist near
the output
2o port. The focusing element can focus the radiation to a waist diameter of
about 1,000
microns or less (e.g., about 500 microns or less). The focusing element can be
a lens.
The lens can include ~nSe.
The apparatus can further include the photonic crystal fiber.
In general, in another aspect, the invention features methods that include
25 modifying a polarization state of radiation emitted from a laser, directing
the radiation
having the modified polarization state into an input end of a photonic crystal
fiber
having a hollow core, and coupling gas from a gas source into the input end of
the
hollow core.
Embodiments of the methods can include one or more of the features or other
3o aspects.
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
In general, in another aspect, the invention features methods that include
guiding radiation through an optical waveguide to tissue of a patient, wherein
the
optical waveguide has a hollow core, and directing gas to the tissue while
guiding the
radiation, wherein the radiation and gas are sufficient to cut (e.g., excise
or ablate) the
tissue and to substantially coagulate exposed blood.
In general, in a further aspect, the invention features a medical laser
system,
including a laser, an optical waveguide having a hollow core, a delivery
device, a gas
source (e.g., a cylinder of gas, a compressor, a blower) configured to deliver
a gas to
the tissue, wherein during operation radiation from the laser and gas from the
gas
1 o source are delivered to tissue of a patient, wherein the radiation and gas
are sufficient
to incise the tissue and substantially coagulate exposed blood.
In general, in another aspect, the invention features a system, including a
laser
having an output terminal, a photonic crystal fiber having an input end and an
output
end, the input end being configured to accept radiation emitted from the
output
15 terminal, and a delivery device for allowing an operator to direct
radiation emitted
from the output end to target tissue.
In general, in another aspect, the invention features a system, including a
C02
laser, an endoscope, and a photonic crystal fiber, wherein during operation
the
photonic crystal fiber guides radiation from the C~Z laser through the
endoscope to
2o target tissue.
In general, in a further aspect, the invention features a coupler for coupling
gas
and radiation into one end of a hollow core of a fiber.
Embodiments of the invention may include one or more of the following
features.
25 The gas can be directed through the hollow core of the optical waveguide or
the gas can be directed to the tissue through a tube separate from the hollow
core.
The radiation can be delivered from a laser (e.g., a COZ laser). The laser can
have an
output power of about 5 Watts or more (e.g., about 10 Watts or more, about 15
Watts
or more, about 20 Watts or more, about 50 Watts or more, about 100 Watts or
more).
3o The radiation delivered to the tissue can have a power of about 1 Watt or
more as
measured at the distal end of the optical waveguide (e.g., about 2 Watts or
more, 5
Watts or more, 8 Watts or more, 10 Watts or more, about 20 Watts or more,
about 50
9
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
Watts or more). The radiation can have a wavelength of about 10.6 microns. The
gas
can have a flow rate of about 1 liter/min or more (e.g., about 2 liter/min or
more,
about 5 liter/min or more, about 8 liter/min or more, about 10 liter/min or
more, about
12 liter/min or more, about 15 liter/min or more, about 20 liter/min or more).
The pressure of the gas exiting the hollow core can be relatively high. For
example, the gas pressure exiting the fiber can correspond to a flow rate of
about 1
liter/min or more (e.g., about 2 liter/min or more, about 5 liter/min or more,
about 8
Iiter/min or more, about 10 Iiter/min or more, about 12 liter/min or more,
about 15
liter/min or more, about 20 liter/min or more) through a 1 meter length of
fiber having
1o a core diameter of about 500 pm.
The gas can include air, nitrogen, oxygen, carbon dioxide or a noble gas
(e.g.,
He, Ne, Ar, Kr, and/or Xe). The gas can include substantially only one
compound
(e.g., about 98% or more of one compound, about 99% or more, about 99.5% or
more,
about 99.8% or more, about 99.9% or more). Alternatively, in some embodiments,
1s the gas can include a mixture of different compounds (e.g., air).
The method can further include excising tissue with the radiation. The optical
waveguide can be a photonic crystal fiber (e.g., a Bragg fiber). The gas can
have a
temperature of about 50°C or more at the tissue (e.g., about
60°C or more, about 70°C
or more, about 80°C or more, about 90°C or more, about
100°C or more). The
2o method can further include bending the fiber while delivering radiation to
the tissue.
The fiber bend can have a radius of curvature of about 12 cm or less (e.g.,
about 10
cm or less, about 8 cm or less, about 7 cm or less, about 6 cm or less, about
5 cm or
less, about 4 cm or less, about 3 cm or less, about 2 cm or less).
A number of references are incorporated herein by reference. In case of
25 conflict, the present application will control.
The details of one or more embodiments of the invention are set forth in the
accompanying drawings and the description below. Other features and advantages
of
the invention will be apparent from the description and drawings, and from the
claims.
to
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
DESCRIPTION OF DRAWINGS
FTG 1 is a schematic diagram of an embodiment of a laser medical system that
includes a photonic crystal fiber.
FIG 2A is a cross-section view of an embodiment of a photonic crystal fiber.
FIG 2B-2D are cross-sectional views of embodiments of confinement regions
for photonic crystal fibers.
FIG 3 is a cross-sectional view of a photonic crystal fiber including a
cladding
having an asymmetric cross-section.
FIG 4A-4D are cross-sectional views of embodiments of sleeves attached to
o an output end of a photonic crystal fiber.
FIG 5A and 5B are diagrams of embodiments of coupling assemblies for
coupling radiation and a fluid into a hollow core of a photonic crystal fiber.
FIG 6 is a diagram of a handpiece that includes a malleable conduit.
FIG 7A is a schematic diagram of another embodiment of a laser medical
15 system including a photonic crystal fiber.
FIG 7B is a diagram of an endoscope.
FIG 7C is a schematic diagram of a further embodiment of a medical laser
system including a photonic crystal fiber.
FIG 8 is a schematic diagram of a portion of a medical laser system that
2o includes a photonic crystal fiber and a second fiber waveguide.
FIG 9 is a schematic diagram of a portion of a medical Iaser system that
includes a photonic crystal fiber and a tube for exhausting fluid from the
fiber.
Like reference symbols in the various drawings indicate like elements.
DETAILED DESCRIPTION
2s Referring to FIG. 1, a medical laser system 100 includes a COa laser 110,
and
a photonic crystal fiber 120 having a hollow core to guide radiation 112 from
the laser
to a target location 99 of a patient. Radiation 112 has a wavelength of 10.6
microns.
Laser radiation 112 is coupled by a coupling assembly 130 into the hollow core
of
photonic crystal fiber 120, which delivers the radiation through a handpiece
140 to
so target location 99. During use, an operator (e.g., a medical practitioner,
such as a
surgeon, a dentist, an ophthalmologist, or a veterinarian) grips a portion 142
of
11
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
handpiece 140, and manipulates the handpiece to direct laser radiation I I3
emitted
from an output end of photonic crystal fiber 120 to target location 99 in
order to
perform a therapeutic function at the target location. For example, the
radiation can
be used to excise, incise, ablate, or vaporize tissue at the target location.
COZ laser 110 is controlled by an electronic controller 150 for setting and
displaying operating parameters of the system. The operator controls delivery
of the
laser radiation using a remote control 152, such as a foot pedal. In some
embodiments, the remote control is a component of handpiece 140, allowing the
operator to control the direction of emitted laser radiation and delivery of
the laser
radiation with one hand or both hands.
In addition to grip portion 142, handpiece 140 includes a stand off tip 144,
which maintains a desired distance (e.g., from about 0.1 millimeters to about
30
millimeters) between the output end of fiber 120 and target tissue 99. The
stand off
tip assist the operator in positioning the output end of photonic crystal
fiber 120 from
1 s target location 99, and can also reduce clogging of the output end due to
debris at the
target location. In some embodiments, handpiece 140 includes optical
components
(e.g., a lens or lenses), which focus the beam emitted from the fiber to a
desired spot
size. The waist of the focused beam can be located at or near the distal end
of the
stand off tip.
2o In some embodiments, fiber 120 can be easily installed and removed from
coupling assembly 130, and from handpiece 140 (e.g., using conventional fiber
optic
connectors). This can facilitate ease of use of the system in single-use
applications,
where the fiber is replaced after each procedure.
Typically, COa laser 110 has an average output power of about 5 Watts to
2s about 80 Watts at 10.6 microns (e.g., about 10 Watts or more, about 20
Watts or
more). In many applications, laser powers of about 5 Watts to about 30 Watts
are
sufficient for the system to perform its intended function. For example, where
system
100 is being used to excise or incise tissue, the radiation is confined to a
small spot
size and a laser having an average output power in this range is sufficient.
3o In certain embodiments, however, laser 110 can have an output power as high
as about 100 Watts or more (e.g., up to about 500 Watts). For example, in
applications where system I00 is used to vaporize tissue over a relatively
large area
12
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
(e.g., several square millimeters or centimeters), extremely high power lasers
may be
desirable.
Photonic crystal fiber can deliver the radiation from laser 110 to the target
location with relatively high efficiency. For example, the fiber average
output power
can be about 50% or more of the fiber input energy (e.g., about 60% or more,
about
70% or more, about 80% or more). Accordingly, the fiber's output power can be
about 3 Watts or more (e.g., about 8 Watts or more, about 10 Watts or more,
about 15
Watts or more). In certain embodiments, however, the average output power from
the
fiber can be less than 50% of the laser power, and still be sufficiently high
to perform
1 o the intended procedure. For example, in some embodiments, the fiber
average output
power can be from about 20% to about 50% of the laser average output power.
The length of photonic crystal fiber 120 can vary as desired. In some
embodiments, the fiber is about 1.2 meters long or more (e.g., about 1.5
meters or
more, about 2 meters or more, about 3 meters or more, about 5 meters or more).
The
~ 5 length is typically dependent on the specific application for which the
laser system is
used. In applications where laser 110 can be positioned close to the patient,
and/or
where the range of motion of the handpiece desired for the application is
relatively
small, the length of the fiber can be relatively short (e.g., about 1.5 meters
or less,
about 1.2 meters or less, about 1 meter or less). In certain applications, the
length of
2o fiber 120 can be very short (e.g., about 50 centimeters or less, about 20
centimeters or
less, about 10 centimeters or less). For example, very short lengths of
photonic
crystal fiber may be useful in procedures where the system can deliver
radiation from
the laser to the fiber by some other means (e.g., a different waveguide or an
articulated arm). Very short fiber lengths may be useful for nose and ear
procedures,
25 for example.
However, in applications where it is inconvenient for the laser to be placed
in
close proximity to the patient and/or where a large range of motion of the
handpiece is
desired, the length of the fiber is longer (e.g., about 2 meters or more,
about 5 meters
or more, about 8 meters or more). For example, in surgical applications, where
a
30 large team of medical practitioners is needed in close proximity to the
patient, it may
be desirable to place the laser away from the operating table (e.g., in the
corner of the
13
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
operating room, or in a different room entirely). In such situations, a longer
fiber may
be desirable.
In general, photonic crystal fiber 120 is flexible, and can be bent to
relatively
small radii of curvature over relatively large angles without significantly
impacting its
performance (e.g., without causing the fiber to fail, or without reducing the
fiber
transmission to a level where the system cannot be used for its intended use
while the
fiber is bent). In some embodiments, an operator can bend photonic crystal
fiber 120
to have a relatively small radius of curvature, such as about 15 cm or less
(e.g., about
cm or less, about 8 cm or less, about 5 cm or less, about 3 cm or less) while
still
1 o delivering sufficient power to the target location for the system to
perform its
function.
In general, the angle through which the fiber is bent can vary, and usually
depends on the procedure being performed. For example, in some embodiments,
the
fibex can be bent through about 90° or more (e.g., about 120° or
more, about 150° or
more).
Losses of transmitted power due to the operator bending photonic crystal fiber
120 may be relatively small. In general, losses due to bends should not
significantly
damage the fiber, e.g., causing it to fail, or reduce the fiber output power
to a level
where the system can no longer perform the function for which it is designed.
2o Embodiments of photonic crystal fiber 120 (e.g., about 1 meter or more in
length) can
be bent through 90° with a bend radius of about 5 centimeters or less,
and still
transmit about 30% or more (e.g., about 50% or more, about 70% or more) of
radiation coupled into the fiber at the guided wavelength. These fibers can
provide
such transmission characteristics and provide average output power of about 3
Watts
or more (e.g., about 5 Watts or more, about 8 Watts or more, about 10 Watts or
more).
The quality of the beam of the laser radiation emitted from the output end of
fiber 120 can be relatively good. For example, the beam can have a low M2
value,
such as about 4 or less (e.g., about 3 or less, about 2.5 or less, about 2 or
less). MZ is a
parameter commonly used to describe laser beam quality, where an M2 value of
about
1 corresponds to a TEMoo beam emitted from a laser, which has a perfect
Gaussian
profile. The MZ value is related to the minimum spot size that can be formed
from the
beam according to the formula:
14
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
ds=1.27f~,M2/db (1)
where ds is the minimum spot diameter, db is the beam diameter prior to being
focused
to the spot by a lens having focal length f. Accordingly, the minimum possible
spot
size a beam can be focused is proportional to the M2 value for the beam.
Practically,
beams having smaller values of M2 can provide higher radiation power densities
to
the target area, with less damage to surrounding tissue due to the decreased
spot size.
The spot size of radiation delivered by photonic crystal fiber 120 to the
target
tissue can be relatively small. For example, in certain embodiments, the spot
can
have a diameter of about 500 microns or less (e.g., about 300 microns or less,
about
200 microns or less, such as about 100 microns) at a desired working distance
from
the fiber's output end (e.g., from about 0.1 mm to about 3 mm). As discussed
previously, a small spot size is desirable where system 100 is being used to
excise or
incise tissue or in other applications where substantial precision in the
delivery of the
radiation is desired. Alternatively, in applications where tissue is to be
ablated or
1s vaporized, and/or a lesser level of precision is sufficient, the spot size
can be
relatively large (e.g., having a diameter of about 2 millimeters or more,
about 3
millimeters or more, about 4 millimeters or more).
While laser 110 is a C02 laser, photonic crystal fibers can be used in medical
laser systems that use other types or lasers, operating at wavelengths
different from
10.6 microns. In general, medical laser systems can provide radiation at
ultraviolet
(LTV), visible, or infrared (IR) wavelengths. Lasers delivering IR radiation,
for
example, emit radiation having a wavelength between about 0.7 microns and
about 20
microns (e.g., between about 2 to about 5 microns or between about 8 to about
12
microns). Waveguides having hollow cores, such as photonic crystal fiber 120,
are
2s well-suited for use with laser systems having wavelengths of about 2
microns or
more, since gases that commonly occupy the core have relatively low
absorptions at
these wavelengths compared to many dielectric materials (e.g., silica-based
glasses
and various polymers). In addition to C02 lasers, other examples of lasers
which can
emit IR radiation include Nd:YAG lasers (e.g., at 1.064 microns), Er:YAG
lasers
so (e.g., at 2.94 microns), Er, Cr: YSGG (Erbium, Chromium doped Yttrium
Scandium
Gallium Garnet) lasers (e.g., at 2.796 microns), Ho:YAG lasers (e.g., at 2.1
microns),
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
free electron lasers (e.g., in the 6 to 7 micron range), and quantum cascade
lasers (e.g.,
in the 3 to 5 micron range).
In general, the type of laser used in a medical laser system depends on the
purpose for which the system is designed. The type of laser can be selected
depending on whether the system is to be used in surgical procedures, in
diagnosis, or
in physiologic studies. For example, an argon laser, which delivers in the
blue and
green regions of the visible light spectrum, with two energy peaks, at 488 nm
and 514
nm, can be used fox photocoagulation. A dye laser, which is a laser with
organic dye
dissolved in a solvent as the active medium whose beam is in the visible light
spectrum, can be used in photodynamic therapy. Excimer lasers provide
radiation in
the ultraviolet spectrum, penetrates tissues only a small distance, can be
used to break
chemical bonds of molecules in tissue instead of generating heat to destroy
tissue.
Such lasers can be used in ophthalmological procedures and laser angioplasty.
Ho:YAG lasers can provide radiation in the near infrared spectrum and can be
used
for photocoagulation and photoablation. Krypton lasers provide radiation in
the
yellow-red visible light spectrum, and can be used for photocoagulation.
Radiation
from KTP lasers can be frequency-doubled to provide radiation in the green
visible
light spectrum and can be used for photoablation and photocoagulation. Nd:YAG
lasers can be for photocoagulation and photoablation. Pulsed dye lasers can be
used
2o to provide in the yellow visible light spectrum (e.g., with a wavelength of
577 nm or
585 nm), with alternating on and off phases of a few microseconds each, and
can be
used to decolorize pigmented lesions.
In general, laser systems can use continuous wave or pulsed lasers.
Furthermore, while CO~ lasers are typically used at average output powers of
about 5
2s Watts to about 100 Watts, photonic crystal fibers can generally be used
with a variety
of laser powers. For example, average laser power can be in the milliWatt
range in
certain systems, up to as much as several hundred Watts (e.g., about 200 Watts
or
more) in extremely high power systems.
In general, for high power systems, the average power density guided by fiber
so 120 can be extremely high. For example, power density in the fiber, or
exiting the
fiber's core) can be about 103 W/cm2 or more (e.g., about 104 W/cm2 or more,
about
105 W/cm2 or more, 106 Wlcm2 or more).
16
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
Referring to FIG. 2A, in general, photonic crystal fiber I20 includes a core
210, which is surrounded by a confinement region 220 extending along a
waveguide
axis 299 (normal to the plane of FIG. 2A). Confinement region 220 is
surrounded by
a cladding 230 (e.g., a polymer cladding), which provides mechanical support
and
protects the core and confinement region from environmental hazards.
Confinement
region 220 includes a photonic crystal structure that substantially confines
radiation at
a wavelength ~, to core 210. Examples of such structures are described with
reference
to FIGS. 2B-2D below. As used herein, a photonic crystal is a structure (e.g.,
a
dielectric structure) with a refractive index modulation (e.g., a periodic
refractive
io index modulation) that produces a photonic bandgap in the photonic crystal.
An
example of such a structure, giving rise to a one dimensional refractive index
modulation, is a stack of dielectric layers of high and low refractive index,
where the
layers have substantially the same optical thickness. A photonic bandgap, as
used
herein, is a range of frequencies in which there are no accessible extended
(i.e.,
propagating, non-localized) states in the dielectric structure. Typically the
structure is
a periodic dielectric structure, but it may also include, e.g., more complex
"quasi-
crystals." The bandgap can be used to confine, guide, and/or localize light by
combining the photonic crystal with "defect" regions that deviate from the
bandgap
structure. Moreover, there are accessible extended states for frequencies both
below
2o and above the gap, allowing light to be confined even in lower-index
regions (in
contrast to index-guided TIR structures). The term "accessible" states means
those
states with which coupling is not already forbidden by some symmetry or
conservation law of the system. For example, in two-dimensional systems,
polarization is conserved, so only states of a similar polarization need to be
excluded
2s from the bandgap. In a waveguide with uniform cross-section (such as a
typical
fiber), the wavevector,(iis conserved, so only states with a given,l3need to
be
excluded from the bandgap to support photonic crystal guided modes. Moreover,
in a
waveguide with cylindrical symmetry, the "angular momentum" index m is
conserved, so only modes with the same m need to be excluded from the bandgap.
In
3o short, for high-symmetry systems the requirements for photonic bandgaps are
17
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
considerably relaxed compared to "complete" bandgaps in which all states,
regardless
of symmetry, are excluded.
Theoretically, a photonic crystal is only completely reflective in the bandgap
when the index modulation in the photonic crystal has an infinite extent.
Otherwise,
s incident radiation can "tunnel" through the photonic crystal via an
evanescent mode
that couples propagating modes on either side of the photonic crystal. In
practice,
however, the rate of such tunneling decreases exponentially with photonic
crystal
thickness (e.g., the number of alternating layers). It also decreases with the
magnitude of the index contrast in the confinement region.
io Furthermore, a photonic bandgap may extend over only a relatively small
region of propagation vectors. For example, a dielectric stack may be highly
reflective for a normally incident ray and yet only partially reflective for
an obliquely
incident ray. A "complete photonic bandgap" is a bandgap that extends over all
possible wavevectors and all polarizations. Generally, a complete photonic
bandgap
15 is only associated with a photonic crystal having index modulations along
three
dimensions. However, in the context of EM radiation incident on a photonic
crystal
from an adjacent dielectric material, we can also define an "omnidirectional
photonic
bandgap," which is a photonic bandgap for all possible wavevectors and
polarizations
for Which the adjacent dielectric material supports propagating EM modes.
2o Equivalently, an omnidirectional photonic bandgap can be defined as a
photonic band
gap for all EM modes above the light line, wherein the light Iine defines the
lowest
frequency propagating mode supported by the material adjacent the photonic
crystal.
For example, in air the light line is approximately given by ev = c,(3, where
w is the
angular frequency of the radiation, ,l3is the wavevector, and c is the speed
of light. A
2s description of an omnidirectional planar reflector is disclosed in U.S.
Patent
6,130,780, the entire contents of which are incorporated herein by reference.
Furthermore, the use of alternating dielectric layers to provide
omnidirectional
reflection (in a planar limit) for a cylindrical waveguide geometry is
disclosed in
Published PCT application WO 00/22466, the contents of which are incorporated
3o herein by reference.
18
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
When confinement region 220 gives rise to an omnidirectional bandgap with
respect to core 210, the guided modes are strongly confined because, in
principle, any
EM radiation incident on the confinement region from the core is completely
reflected. As described above, however, such complete reflection only occurs
when
there are an infinite number of layers. For a finite number of layers (e.g.,
about 20
layers), an omnidirectional photonic bandgap may correspond to a reflectivity
in a
planar geometry of at least 95 % for all angles of incidence ranging from
0° to 80°
and for all polarizations of EM radiation having frequency in the
omnidirectional
bandgap. Furthermore, even when fiber 120 has a confinement region with a
bandgap
that is not omnidirectional, it may still support a strongly guided mode,
e.g., a mode
with radiation losses of less than 0.1 d13/km for a range of frequencies in
the bandgap.
Generally, whether or not the bandgap is omnidirectional will depend on the
size of
the bandgap produced by the alternating layer (which generally scales with
index
contrast of the two layers) and the lowest-index constituent of the photonic
crystal.
15 Regarding the structure of photonic crystal fiber 120, in general, the
diameter
of core 210 (indicated by reference numeral 211 in FIG 2A) can vary depending
on
the end-use application of system 100. For example, where a large spot size is
desired, the core can be relatively large (e.g., about 1 mm or more, about 2
mm or
more). Alternatively, when a small spot size is desired, core diameter 211 can
be
2o much smaller (e.g., about 500 microns or less, about 300 microns or less,
about 200
microns or less, about 100 microns or less).
More generally, where fiber 120 is used in systems with other types of laser,
and/or used to guide wavelengths other than 10.6 microns, the core diameter
depends
on the wavelength or wavelength range of the energy to be guided by the fiber,
and on
25 whether the fiber is a single or multimode fiber. For example, where the
fiber is a
single mode fiber for guiding visible wavelengths (e.g., between about 400 nm
and
about 800 nm) the core radius can be in the sub-micron to several micron range
(e.g.,
from about 0.5 microns to about 5 microns). However, the core radius can be in
the
tens to thousands of microns range (e.g., from about 10 microns to about 2,000
so microns, such as about 500 microns to about 1,000 microns), for example,
where the
fiber is a multimode fiber for guiding TR wavelengths. The core radius can be
about
19
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
5~, or more (e.g., about 10?~ or more, about 20~, or more, about 50~, or more,
about
100 or more), where ~, is the wavelength of the guided energy.
An advantage of photonic crystal fibers is that fibers having small core
diameters can be readily produced since fibers can be drawn from a perform,
preserving the relative proportions of the fiber's cross-sectional structure
while
reducing the dimensions of that structure to small sizes in a controlled
manner.
In photonic crystal fiber 120, core 220 is hollow. Alternatively, in
embodiments where there are no fluids pumped through the core, core 220 can
include any material or combination of materials that are rheologically
compatible
with the materials forming confinement region 220 and that have sufficiently
high
transmission properties at the guided wavelength(s). In some embodiments, core
220
includes a dielectric material (e.g., an amorphous dielectric material), such
as an
inorganic glass or a polymer. In certain embodiments, core 220 can include one
or
more dopant materials, such as those described in U.S. Patent Application
Serial No.
1~ 10/121,452, entitled "HIGH INDEX-CONTRAST FIBER WAVEGUIDES AND
APPLICATIONS," filed April 12, 2002 and now published under Pub. No. US-2003-
0044158-A1, the entire contents of which are hereby incorporated by reference.
Cladding 230 can be formed from a polymer (e.g., an acrylate or silicone
polymer) or other material. Cladding 230 can be formed from a material that is
also
2o used to as part of confinement region 220, which are described below. In
applications
where the cladding comes in contact with a patient, it can be formed from
materials
that conform to FDA standards for medical devices. In these instances,
silicone
polymers, for example, may be particularly suited for use as the cladding
material.
Typically, cladding 230 protects the fiber from external damage. By selecting
the
25 appropriate thickness, composition, and/or structure, cladding 230 can also
be
designed to limit the flexibility of the fiber, e.g., to prevent damage by
small radius of
curvature bends.
In general, the thickness of fiber 120 can vary. The thickness is indicated by
outer diameter (OD) 231 in FIG 2A. OD 231 can be selected so that fiber 120 is
3o compatible with other pieces of equipment. For example, fiber 120 can be
made so
that OD 231 is sufficiently small so that the fiber can be threaded through a
channel in
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
an endoscope or other tool (e.g., OD 231 can be about 2,000 microns or Iess).
In
some embodiments, fiber 120 has a relatively small OD (e.g., about 1,000
microns or
Iess). Narrow fibers can be useful in applications where they are to be
inserted into
narrow spaces, such as through a patient's urethra. Alternatively, in some
s embodiments, diameter 231 can be relatively large compared (e.g., about
3,000
microns or more). Large OD's can reduce the mechanical flexibility of the
fiber,
which can prevent the fiber from bending to small radii of curvature that
damage the
fiber or reduce its transmission to a level where the system can no longer
perform its
intended function.
1 o In addition to cladding 230, fiber 200 may include additional components
to
Iimit bend radii. For example, the fiber may include a spirally wound material
around
its outer diameter (e.g., a spirally wound wire). Alternatively, or
additionally, the fiber
may include additional claddings to provide additional mechanical support.
Although the fiber can be bent (as discussed above), in some embodiments,
~ s the fiber may be constrained from bending to radii of curvature of less
than about 20
cm (e.g., about 10 cm or less, 8 crn or less, 5 cm or less) during regular use
in the
application for which it is designed.
The cladding material may be selected so that the fiber is sterilizable. For
example, the cladding material may be selected so that the fiber can withstand
high
2o temperatures (e.g., those experienced in an autoclave).
Turning to the structure and composition of confinement region 220, in some
embodiments, photonic crystal fiber I20 is a Bragg fiber and confinement
region 220
includes multiple alternating layers having high and low refractive indexes,
where the
high and low index layers have similar optical thickness. For example,
referring to
25 FIG. 2B, in some embodiments, confinement region 220A includes multiple
annular
dielectric layers of differing refractive index (i.e., layers composed of a
high index
material having a refractive index nH, and layers composed of a low index
material
having a refractive index nL), indicated as layers 212, 213, 214, 215, 216,
217, 218,
219, 222, and 223. Here, nH > nL and nH - nL can be, for example, about 0.01
or more,
so about 0.05 or more, about 0.1 or more, about 0.2 or more, about 0.5 or
more. For
convenience, only a few of the dielectric confinement layers are shown in FIG.
2B. In
practice, confinement region 220A may include many more layers (e.g., about 15
21
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
layers or more, about 20 layers or more, about 30 layers or more, about 40
layers or
more, about 50 layers or more, about 80 layers or more).
In some embodiments, confinement region 220 can give rise to an
omnidirectional bandgap with respect to core 210, wherein the guided modes are
strongly confined because, in principle, any EM radiation incident on the
confinement
region from the core is completely reflected. However, such complete
reflection only
occurs when there are an infinite number of layers. For a finite number of
layers (e.g.,
about 20 layers), an omnidirectional photonic bandgap may correspond to a
reflectivity in a planar geometry of at least 95 % for all angles of incidence
ranging
o from 0° to 80° and for all polarizations of EM radiation
having frequency in the
omr~idirectional bandgap. Furthermore, even when fiber 120 has a confinement
region with a bandgap that is not omnidirectional, it may still support a
strongly
guided mode, e.g., a mode with radiation losses of less than 0.1 dB/km for a
range of
frequencies in the bandgap. Generally, whether or not the bandgap is
omnidirectional
will depend on the size of the bandgap produced by the alternating layers
(which
generally scales with index contrast of the two layers) and the lowest-index
constituent of the photonic crystal.
The existence of an omnidirectional bandgap, however, may not be necessary
for useful application of fiber 120. For example, in some embodiments, a laser
beam
2o used to establish the propagating field in the fiber is a TEMoo mode. This
mode can
couple with high efficiency to the HEII mode of a suitably designed fiber.
Thus, for
successful application of the fiber for transmission of laser energy, it may
only be
necessary that the loss of this one mode be sufficiently low. More generally,
it may
be sufficient that the fiber support only a number of low loss modes (e.g.,
the HEl l
mode and the modes that couple to it from simple perturbations, such as
bending of
the fiber). In other words, photonic bandgap fibers may be designed to
minimize the
losses of one or a group of modes in the fiber, without necessarily possessing
an
omnidirectional bandgap.
For a planar dielectric reflector, it is well-known that, for normal
incidence, a
so maximum band gap is obtained for a "quarter-wave" stack in which each layer
has
equal optical thickness ~,/4, or equivalently n,,;d~; = n,od,o = ~ , where
dh;,~o and n,,;ilo
22
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
refer to the thickness and refractive index, respectively, of high-index and
low-index
layers in the stack. Normal incidence, however, corresponds to ~3=0, whereas
for a
cylindrical waveguide the desired modes typically lie near the light line ~c/3
(in the
limit of large R, the lowest-order modes are essentially plane waves
propagating along
s z-axis, i.e., the waveguide axis). In this case, the quarter-wave condition
becomes:
dn~ ~~2 ~1= do jZU2 -1= ~ (2)
This equation may not be exactly optimal because the quarter-wave condition
is modified by the cylindrical geometry, which may require the optical
thickness of
each layer to vary smoothly with its radial coordinate. In addition, the
differing
1 o absorption of the high and low index materials can change the optimal
layer
thicknesses from their quarter-wave values.
In certain embodiments, confinement region 220 includes layers that do not
satisfy the quarter-wave condition given in Eq. 2. In other words, for the
example
shown in FIG 2B, one or more of layers 212, 213, 214, 215, 216, 217, 218, 219,
222,
15 and 223 are thicker or thinner than d~4, where d~,,4 = 4 ~ -1 , and n is
the refractive
index of the layer (i.e., d~,4 corresponds to an optical thickness equal to
the quarter-
wave thickness). For example, one or more layers in the confinement region can
have
a thickness of about 0.9 d~4 or less (e.g., about 0.8 d~,4 or less, about 0.7
d~,~. or less,
about 0.6 d~,4 or less, about 0.5 d~,4 or less, about 0.4 d~,4 or less, about
0.3 d~,4 or
20 less), or about 1.1 d~,4 or more (e.g., about 1.2 d~,4 or more, about 1.3
d~,4 or more,
about 1.4 d~,4 or more, about 1.5 d~,4 or more, about 1.8 d~,4 or more, about
2.0 d~,4 or
more). In some embodiments, all layers in the confinement region can be
detuned
from the quarter-wave condition. In some embodiments, the thickness of one or
more
of the high index layers can be different (e.g., thicker or thinner) from the
thickness of
2s the other high index layers. For example, the thickness of the innermost
high index
layer can be different from the thickness of the other high index layers.
Alternatively,
or additionally, the thickness of one or more of the low index layers can be
different
(e.g., thicker or thinner) from the thickness of the other low index layers.
For
example, the thickness of the innermost low index layer can be different from
the
so thickness of the other low index layers.
23
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
Detuning the thickness of layers in the confinement region from the quarter-
wave condition can reduce the attenuation of photonic crystal fiber 120
compared to a
test fiber, which refers to a fiber identical to photonic crystal fiber 120,
except that the
quarter-wave condition is satisfied for all layers in the confinement region
(i.e., the
s test fiber has an identical core, and its confinement region has the same
number of
layers with the same composition as photonic crystal fiber 120). For example,
fiber
120 can have an attenuation for one or more guided modes that is reduced by a
factor
of about two or more compared to the attenuation of the test fiber (e.g.,
reduced by a
factor of about three or more, about four or more, about five or more, about
ten or
i o more, about 20 or more, about 50 or more, about 100 or more). Examples of
photonic
crystal fibers illustrating reduce attenuation are described in U.S. Patent
Application
Serial No. 10/978,605, entitled "PHOTONIC CRYSTAL WAVEGUIDES AND
SYSTEMS USING SUCH WAVEGU1DES," filed on November 1, 2004, the entire
contents of which is hereby incorporated by reference.
15 The thickness of each layer in the confinement region can vary depending on
the composition and structure of the photonic crystal fiber. Thickness can
also vary
depending on the wavelength, mode, or group of modes for which the photonic
crystal
fiber is optimized. The thickness of each layer can be determined using
theoretical
and/or empirical methods. Theoretical methods include computational modeling.
2o One computational approach is to determine the attenuation of a fiber for
different
layer thicknesses and use an optimization routine (e.g., a non-linear
optimization
routine) to determine the values of layer thickness that minimize the fiber's
attenuation for a guided mode. For example, the "downhill simplex method",
described in the text Numerical Recipes in FORTRAN (second edition), by W.
Press,
2s S. Teukolsky, W. Vetterling, and B Flannery, can be used to perform the
optimization.
Such a model should account for different attenuation mechanisms in a fiber.
Two mechanisms by which energy can be lost from a guided EM mode are by
absorption loss and radiation loss. Absorption loss refers to loss due to
material
absorption. Radiation loss refers to energy that leaks from the fiber due to
imperfect
3o confinement. Both modes of loss contribute to fiber attenuation and can be
studied
theoretically, for example, using transfer matrix methods and perturbation
theory. A
discussion of transfer matrix methods can be found in an article by P Yeh et
al., J.
24
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
Opt. Soc. Am., 68, p. 1196 (1978). A discussion of perturbation theory can
found in
an article by M. Skorobogatiy et al., Optics Express, 10, p. 1227 (2002).
Particularly,
the transfer matrix code finds propagation constants ,(3 for the "leaky" modes
resonant
in a photonic crystal fiber structure. Imaginary parts of ,(3's define the
modal radiation
loss, thus LOSSradiation ~ ~~~ Loss due to material absorption is calculated
using
perturbation theory expansions, and in terms of the modal field overlap
integral it can
be determined from
LossnvsarNno" ~ 2~'CO f Ydt-(aE~E~), (3)
0
where ev is the radiation frequency, r is the fiber radius, ais bulk
absorption of the
1 o material, and E~ is an electric field vector.
Alternatively, the desired mode fields that can propagate in the fiber can be
expanded in a suitable set of functions, such as B-splines (see, e.g., A
Practical Guide
to Splines, by C. deBoor). Application of the Galerkin conditions (see, e.g.,
Computational Galerkin Methods, C.A.J. Fletcher, Springer-Verlag, 1984) then
1 s converts Maxwell's equations into a standard eigenvalue-eigenvector
problem, which
can be solved using the LAPACI~ software package (freely available, for
example,
from the netlib repository on the Internet, at "http://www.netlib.org"). The
desired
complex propagation constants, containing both material and radiation losses,
are
obtained directly from the eigenvalues.
2o Guided modes can be classified as one of three types: pure transverse
electric
(TE); pure transverse magnetic (TM); and mixed modes. Loss often depends on
the
type of mode. For example, TE modes can exhibit lower radiation and absorption
losses than TM/mixed modes. Accordingly, the fiber can be optimized for
guiding a
mode that experiences low radiation and/or absorption loss.
25 While confinement region 220A includes multiple annular layers that give
rise
to a radial refractive index modulation, in general, confinement regions can
also
include other structures to provide confinement properties. For example,
referring to
FIG. ZC, a confinement region 220B includes continuous layers 240 and 250 of
dielectric material (e.g., polymer, glass) having different refractive
indices, as
30 opposed to multiple discrete, concentric layers. Continuous layers 240 and
250 form
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
a spiral around axis 299. One or more of the layers, e.g., layer 240 is a high-
index
layer having an index nH and a thickness d~, and the layer, e.g., layer 250,
is a low-
index layer having an index fZL and a thickness dL, where faH > nL (e.g., nH -
nL can be
about 0.01 or more, about 0.05 or more, about 0.1 or more, about 0.2 or more,
about
0.5 or more).
Because layers 240 and 250 spiral around axis 199, a radial section extending
from axis 199 intersects each of the layers more than once, providing a radial
profile
that includes alternating high index and low index layers.
The spiraled layers in confinement region 220B provide a periodic variation in
1 o the index of refraction along a radial section, with a period
corresponding to the
optical thickness of layers 240 and 250. In general, the radial periodic
variation has
an optical period corresponding t0 122404240 'E' j2250d250~
The thickness (d2ao and d2so) and optical thickness (~Zaodaao and n2sodaso) of
layers 240 and 250 are selected based on the same considerations as discussed
for
confinement region 220A above.
For the embodiment shown in FIG. 2C, confinement region 220B is 5 optical
periods thick. In practice, however, spiral confinement regions may include
many
more optical periods (e.g., about 8 optical periods or more, about 10 optical
periods or
more, about 15 optical periods or more, about 20 optical periods or more,
about 25
optical periods or more, such as about 40 or more optical periods).
Fiber's having spiral confinement regions can be formed from a spiral perform
by rolling a planar multilayer film into a spiral and consolidating the spiral
by fusing
(e.g., by heating) the adjacent layers of the spiral together. In some
embodiments, the
planar multilayer film can be rolled into a spiral around a mandrel (e.g., a
glass
cylinder or rod), and the mandrel can be removed (e.g., by etching or by
separating
the mandrel from the spiral sheath and slipping it out of the sheath) after
consolidation
to provide the spiral cylinder. The mandrel can be formed from a single
material, or
can include portions of different materials. For example, in some embodiments,
the
mandrel can be coated with one or more layers that are not removed after
so consolidation of the rolled spiral structure. As an example, a mandrel can
be formed
from a first material (e.g., a silicate glass) in the form of a hollow rod,
and a second
material (e.g., another glass, such as a chalcogenide glass) coated onto the
outside of
26
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
the hollow rod. The second material can be the same as one of the materials
used to
form the multilayer film. After consolidation, the first material is etched,
and the
second material forms part of the fiber preform.
In some embodiments, additional material can be disposed on the outside of
s the wrapped multilayer film. For example, a polymer film can be wrapped
around the
outside of the spiral, and subsequently fused to the spiral to provide an
annular
polymer layer (e.g., the cladding). In certain embodiments, both the
multilayer film
and an additional film can be wrapped around the mandrel and consolidated in a
single fusing step. In embodiments, the multilayer film can be wrapped and
1 o consolidated around the mandrel, and then the additional film can be
wrapped around
the fused spiral and consolidated in a second fusing step. The second
consolidation
can occur prior to or after etching the mandrel. Optionally, one or more
additional
layers can be deposited (e.g., using CVD) within the spiral prior to wrapping
with the
additional film.
15 Methods for preparing spiral articles are described in U.S. Patent
Application
Serial No. 10/733,873, entitled "FIBER WAVEGUIDES AND METHODS OF
MAKING SAME," filed on December 10, 2003, the entire contents of which are
hereby incorporated by reference.
Referring to FIG. 2D, in some embodiments, photonic crystal fiber 120 can
2o include a confinement region 2200 that includes a spiral portion 260 and an
annular
portion 270. The number of layers in annular portion 270 and spiral portion
260
(along a radial direction from the fiber axis) can vary as desired. In some
embodiments, annular portion can include a single layer. Alternatively, as
shown in
Fig. 2D, annular portion 270 can include multiple layers (e.g., two or more
layers,
2s three or more layers, four or more layers, five or more layers, ten or more
layers).
In embodiments where annular portion 270 includes more than one layer, the
optical thickness of each layer may be the same or different as other layers
in the
annular portion. In some embodiments, one or more of the layers in annular
portion
270 may have an optical thickness corresponding to the quarter wave thickness
(i.e.,
so as given by Eq. (2). Alternatively, or additionally, one or more layers of
annular
portion 270 can have a thickness different from the quarter wave thickness.
Layer
27
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
thickness can be optimized to reduce (e.g., minimize) attenuation of guided
radiation
using the optimization methods disclosed herein.
In certain embodiments, annular portion 270 can be formed from materials
that have relatively low concentrations of defects that would scatter and/or
absorb
s radiation guided by photonic crystal fiber 120. For example, annular portion
270 can
include one or more glasses with relatively low concentrations of
inhomogeneities
and/or impurities. Inhomogeneities and impurities can be identified using
optical or
electron microscopy, for example. Raman spectroscopy, glow discharge mass
spectroscopy, sputtered neutrals mass spectroscopy or Fourier Transform
Infrared
1 o spectroscopy (FTIR) can also be used to monitor inhomogeneities and/or
impurities in
photonic crystal fibers.
In certain embodiments, annular portion 270 is formed from materials with a
lower concentration of defects than spiral portion 260. In general, these
defects
include both structural defects (e.g., delamination between layers, cracks)
and
is material inhomogeneities (e.g., variations in chemical composition and/or
crystalline
structure).
Fibers having confinement regions such as shown in FIG. 2D can be prepared
by depositing one or more annular layers onto a surface of a cylinder having a
spiral
cross-section to form a preform. The photonic crystal fiber can then be drawn
from
2o the preform.
Annular layers can be deposited onto a surface of the spiral cylinder using a
variety of deposition methods. For example, where the spiral portion is
between the
annular portion and the core, material can be evaporated or sputtered onto the
outer
surface of the spiral article to form the preform.
2s In embodiments where the annular portion of the photonic crystal fiber is
between the spiral portion and the core, material can be deposited on the
inner surface
of the spiral article by, for example, chemical vapor deposition (e.g., plasma
enhanced
chemical vapor deposition). Methods for depositing layers of, for example, one
or
more glasses onto an inner surface of a cylindrical preform are described in
U.S.
so Patent Application Serial No. 10/720,453, entitled "DIELECTRIC WAVEGUIDE
AND METHOD OF MAKING THE SAME," filed on November 24, 2003, the entire
contents of which are hereby incorporated by reference.
28
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
In general, a confinement region may include photonic crystal structures
different from a multilayer configuration. For example, confinement region
220C
includes both a spiral portion and annular portion, in some embodiments,
confinement
regions can include portions with other non-spiral structure. For example, a
s confinement region can include a spiral portion and a holey portion (e.g.,
composed of
a solid cylinder perforated by a number of holes that extend along the fiber's
axis).
The holes can be arranged along concentric circles, providing a variation in
the radial
refractive index of the holey portion of the confinement region.
With regard to the composition of confinement region 220, the composition of
1o high index and low index layers are typically selected to provide a desired
refractive
index contrast between the layers at the fiber's operational wavelength(s).
The
composition of each high index layer can be the same or different as other
high index
layers, just as the composition of each low index layer can be the same or
different as
other low index layers.
15 Suitable materials for high and low index layers can include inorganic
materials such as inorganic glasses or amorphous alloys. Examples of inorganic
glasses include oxide glasses (e.g., heavy metal oxide glasses), halide
glasses and/or
chalcogenide glasses, and organic materials, such as polymers. Examples of
polymers
include acrylonitrile-butadiene-styrene (ABS), poly methylmethacrylate (PMMA),
2o cellulose acetate butyrate (CAB), polycarbonates (PC), polystyrenes (PS)
(including,
e.g., copolymers styrene-butadiene (SBC), methylestyrene-acrylonitrile,
styrene-
xylylene, styrene-ethylene, styrene -propylene, styrene-acylonitrile (SAN)),
polyetherimide (PEI), polyvinyl acetate (PVAC), polyvinyl alcohol (PVA),
polyvinyl
chloride (PVC), polyoxymethylene; polyformaldehyde (polyacetal) (POM),
ethylene
2s vinyl acetate copolymer (EVAC), polyamide (PA), polyethylene terephthalate
(PETP), fluoropolymers (including, e.g., polytetrafluoroethylene (PTFE),
polyperfluoroalkoxythylene (PFA), fluorinated ethylene propylene (FEP)),
polybutylene terephthalate (PBTP), low density polyethylene (PE),
polypropylene
(PP), poly methyl pentanes (PMP) (and other polyolefins, including cyclic
so polyolefins), polytetrafluoroethylene (PTFE), polysulfides (including,
e.g.,
polyphenylene sulfide (PPS)), and polysulfones (including, e.g., polysulfone
(PSU),
polyehtersulfone (PES), polyphenylsulphone (PPSU), polyarylalkylsulfone, and
29
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
polysulfonates). Polymers can be homopolymers or copolymers (e.g.,
(Co)poly(acrylamide-acrylonitrile) and/or acrylonitrile styrene copolymers).
Polymers can include polymer blends, such as blends of polyamides-polyolefins,
polyamides-polycarbonates, and/or PES-polyolefins, for example.
s Further examples of polymers that can be used include cyclic olefin polymers
(COPs) and cyclic olefin copolymers (COCs). In some embodiments, COPs and
COCs can be prepared by polymerizing norbornen monomers or copolymerization
norbornen monomers and other polyolefins (polyethylene, polypropylene).
Commercially-available COPs and/or COCs can be used, including, for example,
1 o Zeonex n polymers (e.g., Zeonex° E48R) and Zeonor°
copolymers (e.g., Zeonor
1600), both available from Zeon Chemicals L.P. (Louisville, KY). COCs can also
be
obtained from Promerus LLC (Brecksville, OH) (e.g., such as FS1700).
Alternatively, or additionally, low-index regions may be fabricated by using
hollow structural support materials, such as silica spheres or hollow fibers,
to separate
15 high-index layers or regions. Examples of fibers that include such
structural supports
are described in Published International Application WO 03/058308, entitled
"BIREFRINGENT OPTICAL FIBRES," the entire contents of which are hereby
incorporated by reference.
In certain embodiments, the confinement region is a dielectric confinement
2o region, being composed of substantially all dielectric materials, such as
one or more
glasses and/or one or more dielectric polymers. Generally, a dielectric
confinement
region includes substantially no metal layers.
In some embodiments, the high index layers or low index layers of the
confinement region can include chalcogenide glasses (e.g., glasses containing
a
2s chalcogen element, such as sulphur, selenium, and/or tellurium). In
addition to a
chalcogen element, chalcogenide glasses may include one or more of the
following
elements: boron, aluminum, silicon, phosphorus, sulfur, gallium, germanium,
arsenic,
indium, tin, antimony, thallium, lead, bismuth, cadmium, lanthanum and the
halides
(fluorine, chlorine, bromide, iodine).
so Chalcogenide glasses can be binary or ternary glasses, e.g., As-S, As-Se,
Ge-
S, Ge-Se, As-Te, Sb-Se, As-S-Se, S-Se-Te, As-Se-Te, As-S-Te, Ge-S-Te, Ge-Se-
Te,
Ge-S-Se, As-Ge-Se, As-Ge-Te, As-Se-Pb, As-S-Tl, As-Se-TI, As-Te-Tl, As-Se-Ga,
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
Ga-La-S, Ge-Sb-Se or complex, mufti-component glasses based on these elements
such as As-Ga-Ge-S, Pb-Ga-Ge-S, etc. The ratio of each element in a
chalcogenide
glass can be varied.
In certain embodiments, in addition or alternative to chalcogenide glass(es),
one or more layers in confinement region 220 can include one or more oxide
glasses
(e.g., heavy metal oxide glasses), halide glasses, amorphous alloys, or
combinations
thereof.
In general, the absorption of the high and low index layers varies depending
on their composition and on the fiber's operational wavelength(s). In some
1 o embodiments, the material forming both the high and low index layers can
have low
absorption. A low absorption material has absorption of about 100 dB/m or less
at the
wavelength of operation (e.g., about 20 dB/m or less, about 10 dB/m or less,
about 5
dB/m or less, about 1 dB/m or less, 0.1 dB/m or less). Examples of low
absorption
materials include chalcogenide glasses, which, at wavelengths of about 3
microns,
exhibit an absorption coefficient of about 4 dB/m. At wavelengths of about
10.6
microns, chalcogenide glasses exhibit an absorption coefficient of about 10
dB/m. As
another example, oxide glasses (e.g., lead borosilicate glasses, or silica)
can have low
absorption for wavelengths between about 1 and 2 microns. Some oxide glasses
can
have an absorption coefficient of about 1 dB/m to 0.0002 dB/m in this
wavelength
2o range.
Alternatively, one or both of the high and Iow index materials can have high
absorption (e.g., about 100 dB/m or more, such as about 1,000 or more, about
10,000
or more, about 20,000 or more, about 50,000 dB/m or more). For example, many
polymers exhibit an absorption coefficient of about 105 dB/m for wavelengths
between about 3 and about 11 microns. Examples of such polymers include
polyetherimide (PEI), polychlorotrifluoro ethylene (PCTFE),
perfluoroalkoxyethylene
(PFA), and polyethylene naphthalate (PEN). PEI has an absorption of more than
about 10S dB/m at 3 microns, while PCTFE, PFA, and PEN have absorptions of
more
than about 105 dB/m at 10.6 microns.
3o In some embodiments, the high index material has a low absorption
coefficient
and the Iow absorption material has a high absorption coefficient, or vice
versa.
31
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
A material's absorption can be determined by measuring the relative
transmission through at least two different thicknesses, Tl and TZ, of the
material.
Assuming the field in the material decays with thickness T according to Pe''~
, with P
representing the power incident on the material, the measured transmitted
power
s through thicknesses Ti and T2 will then be P = Pe'~''' and PZ = Pe''~2 . The
absorption coefficient a is then obtained as c~ _ - 1 ln~P2 / Pl ) . If
desired, a
Z'2 ' Z'i
more accurate evaluation of a can be obtained by using several thicknesses and
performing a least squares fit to the logarithm of the transmitted power.
As discussed previously, materials can be selected for the confinement region
to provide advantageous optical properties (e.g., low absorption with
appropriate
indices of refraction at the guided wavelength(s)). However, the materials
should also
be compatible with the processes used to manufacture the fiber. In some
embodiments, the high and low index materials should preferably be compatible
for
co-drawing. Criteria for co-drawing compatibility are provided in
aforementioned
U.S. Patent Application Serial No. 10/121,452, entitled "HIGH INDEX-CONTRAST
FIBER WAVEGUTDES AND APPLICATIONS." In addition, the high and low
index materials should preferably be sufficiently stable with respect to
crystallization,
phase separation, chemical attack and unwanted reactions for the conditions
(e.g.,
environmental conditions such as temperature, humidity, and ambient gas
2o environment) under which the fiber is formed, deployed, and used.
When making a robust fiber waveguides using a drawing process, not every
combination of materials with desired optical properties is necessarily
suitable.
Typically, one should select materials that are Theologically, thermo-
mechanically,
and physico-chemically compatible. Several criteria for selecting compatible
25 materials will now be discussed.
A first criterion is to select materials that are Theologically compatible. In
other words, one should select materials that have similar viscosities over a
broad
temperature range, corresponding to the temperatures experience during the
different
stages of fiber drawing and operation. Viscosity is the resistance of a fluid
to flow
so under an applied shear stress. Here, viscosities are quoted in units of
Poise. Before
32
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
elaborating on Theological compatibility, it is usefule define a set of
characteristic
temperatures for a given material, which are temperatures at which the given
material
has a specific viscosity.
The annealing point, Ta, is the temperature at which a material has a
viscosity
s 1013 Poise. Ta can be measured using a Model SP-2A System from Orton Ceramic
Foundation (Westerville, OH). Typically, Ta is the temperature at which the
viscosity
of a piece of glass is low enough to allow for relief of residual stresses.
The softening point, TS, is the temperature at which a material has a
viscosity
10~'6S Poise. TS can be measured using a softening point instrument, e.g.,
Model SP
3A from Orton Ceramic Foundation (Westerville, OH). The softening point is
related
to the temperature at which the materials flow changes from plastic to viscous
in
nature.
The working point, T",, is the temperature at which a material has a viscosity
104 Poise. Tw can be measured using a glass viscometer, e.g., Model SP-4A from
Orton Ceramic Foundation (Westerville, OH). The working point is related to
the
temperature at which a glass can be easily drawn into a fiber. In some
eriibodiments,
for example, where the material is an inorganic glass, the material's working
point
temperature can be greater than 250°C, such as about 300°C,
400°C, 500°C or more.
The melting point, T,n, is the temperature at which a material has a viscosity
102 Poise. T", can also be measured using a glass viscometer, e.g., Model SP-
4A from
Orton Ceramic Foundation (Westerville, OH). The melting point is related to
the
temperature at which a glass becomes a liquid and control of the fiber drawing
process with respect to geometrical maintenance of the fiber becomes very
difficult.
To be Theologically compatible, two materials should have similar viscosities
2s over a broad temperature range, e.g., from the temperature at which the
fiber is drawn
down to the temperature at which the fiber can no longer release stress at a
discernible
rates (e.g., at Ta) or lower. Accordingly, the working temperature of two
compatible
materials should be similar, so that the two materials flow at similar rates
when
drawn. For example, if one measures the viscosity of the first material,
r~l(T) at the
so working temperature of the second material, TW2, y(T~,,2) should be at
least 103 Poise,
e.g.,104 Poise or 105 Poise, and no more than 10' Poise. Moreover, as the
drawn fiber
33
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
cools the behavior of both materials should change from viscous to elastic at
similar
temperatures. In other words, the softening temperature of the two materials
should
be similar. For example, at the softening temperature of the second material,
TS2, the
viscosity of the first material, r~l(TS2) should be at least 10~ Poise, e.g.,
10' Poise or
108 Poise and no more than 109 Poise. In preferred embodiments, it should be
possible to anneal both materials together, so at the annealing temperature of
the
second material, Ta2, the viscosity of the first material, r~1(Ta2) should be
at least 108
Poise (e.g., at least 10~ Poise, at least 101° Poise, at least 1011
Poise, at least 1012
Poise, at least 1013 Poise, at least 1014 Poise).
1 o Additionally, to be rheologically compatible, the change in viscosity as a
function of temperature (i.e., the viscosity slope) for both materials should
preferably
match as close as possible.
A second selection criterion is that the thermal expansion coefficients (TEC)
of each material should be similar at temperatures between the annealing
temperatures
and room temperature. In other words, as the fiber cools and its rheology
changes
from liquid-like to solid-like, both materials' volume should change by
similar
amounts. If the two materials TEC's are not sufficiently matched, a large
differential
volume change between two fiber portions can result in a large amount of
residual
stress buildup, which can cause one or more portions to crack and/or
delaminate.
2o Residual stress may also cause delayed fracture even at stresses well below
the
material's fracture stress.
The TEC is a measure of the fractional change in sample length with a change
in temperature. This parameter can be calculated for a given material from the
slope
of a temperature-length (or equivalently, temperature-volume) curve. The
temperature-length curve of a material can be measured using e.g., a
dilatometer, such
as a Model 1200D dilatometer from Orton Ceramic Foundation (Westerville, OH).
The TEC can be measured either over a chosen temperature range or as the
instantaneous change at a given temperature. This quantity has the units
°C-1.
For many materials, there are two linear regions in the temperature-length
3o curve that have different slopes. There is a transition region where the
curve changes
from the first to the second linear region. This region is associated with a
glass
34
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
transition, where the behavior of a glass sample transitions from that
normally
associated with a solid material to that normally associated with a viscous
fluid. This
is a continuous transition and is characterized by a gradual change in the
slope of the
temperature-volume curve as opposed to a discontinuous change in slope. A
glass
transition temperature, Tg, can be defined as the temperature at which the
extrapolated
glass solid and viscous fluid lines intersect. The glass transition
temperature is a
temperature associated with a change in the materials rheology from a brittle
solid to a
solid that can flow. Physically, the glass transition temperature is related
to the
thermal energy required to excite various molecular translational and
rotational modes
1 o in the material. The glass transition temperature is often taken as the
approximate
annealing point, where the viscosity is 1013 Poise, but in fact, the measured
T~ is a
relative value and is dependent upon the measurement technique.
A dilatometer can also be used to measure a dilatometric softening point, Tds.
A dilatometer works by exerting a small compressive load on a sample and
heating
the sample. When the sample temperature becomes sufficiently high, the
material
starts to soften and the compressive load causes a deflection in the sample,
when is
observed as a decrease in volume or length. This relative value is called the
dilatometric softening point and usually occurs when the materials viscosity
is
between 10'° and lOla.s poise. The exact Tds value for a material is
usually dependent
2o upon the instrument and measurement parameters. When similar instruments
and
measurement parameters are used, this temperature provides a useful measure of
different materials rheological compatibility in this viscosity regime.
As mentioned above, matching the TEC is an important consideration for
obtaining fiber that is free from excessive residual stress, which can develop
in the
fiber during the draw process. Typically, when the TEC's of the two materials
are not
sufficiently matched, residual stress arises as elastic stress. The elastic
stress
component stems from the difference in volume contraction between different
materials in the fiber as it cools from the glass transition temperature to
room
temperature (e.g., 25°C). The volume change is determined by the TEC
and the
3o change in temperature. For embodiments in which the materials in the fiber
become
fused or bonded at any interface during the draw process, a difference in
their
respective TEC's will result in stress at the interface. One material will be
in tension
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
(positive stress) and the other in compression (negative stress), so that the
total stress
is zero. Moderate compressive stresses themselves are not usually a major
concern
for glass fibers, but tensile stresses are undesirable and may lead to failure
over time.
FIence, it is desirable to minimize the difference in TEC's of component
materials to
s minimize elastic stress generation in a fiber during drawing. For example,
in a
composite fiber formed from two different materials, the absolute difference
between
the TEC's of each glass between Tg and room temperature measured with a
dilatometer with a heating rate of 3 °Clmin, should be no more than
about 5x10-~ °C-1
(e.g., no more than about 4x10-6 °C-1, no more than about 3x10-6
°C-1, no more than
1o about 2x10-6 °C-1, no more than about 1x106 °C-1, no more
than about 5x10- °C-1, no
more than about 4x10- °C-1, no more than about 3x10- °C-1, no
more than about
2x10- °C-1).
While selecting materials having similar TEC's can minimize an elastic stress
component, residual stress can also develop from viscoelastic stress
components. A
1 s viscoelastic stress component arises when there is sufficient difference
between strain
point or glass transition temperatures of the component materials. As a
material cools
below Tg it undergoes a sizeable volume contraction. As the viscosity changes
in this
transition upon cooling, the time needed to relax stress increases from zero
(instantaneous) to minutes. For example, consider a composite preform made of
a
2o glass and a polymer having different glass transition ranges (and different
Ti's).
During initial drawing, the glass and polymer behave as viscous fluids and
stresses
due to drawing strain are relaxed instantly. After leaving the hottest part of
the draw
furnace, the fiber rapidly loses heat, causing the viscosities of the fiber
materials to
increase exponentially, along with the stress relaxation time. Upon cooling to
its Tg,
2s the glass and polymer cannot practically release any more stress since the
stress
relaxation time has become very large compared with the draw rate. So,
assuming the
component materials possess different T~ values, the first material to cool to
its T~ can
no longer reduce stress, while the second material is still above its Tb, and
can release
stress developed between the materials. Once the second material cools to its
T~,
3o stresses that arise between the materials can no longer be effectively
relaxed.
Moreover, at this point the volume contraction of the second glass is much
greater
than the volume contraction of the first material (which is now below its Tg
and
36
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
behaving as a brittle solid). Such a situation can result sufficient stress
buildup
between the glass and polymer so that one yr both of the portions mechanically
fail.
This leads us to a third selection criterion for choosing fiber materials: it
is desirable
to minimize the difference in Tg's of component materials to minimize
viscoelastic
stress generation in a fiber during drawing. Preferably, the glass transition
temperature of a first material, Tgr, should be within 100°C of the
glass transition
temperature of a second material, T~Z (e.g., ITgI -T~ZI should be less than
90°C, less
than ~0°C, less than 70°C, less than 60°C, less than
50°C, less than 40°C, less than
30°C, less than 20°C, less than 10°C).
1o Since there are two mechanisms (i.e., elastic and viscoelastic) to develop
permanent stress in drawn fibers due to differences between constituent
materials,
these mechanisms may be employed to offset one another. For example, materials
constituting a fiber may naturally offset the stress caused by thermal
expansion
mismatch if mismatch in the materials Tg's results in stress of the opposite
sign.
Conversely, a greater difference in T~ between materials is acceptable if the
materials'
thermal expansion will reduce the overall permanent stress. One way to assess
the
combined effect of thermal expansion and glass transition temperature
difference is to
compare each component materials' temperature-length curve. After finding Tg
for
each material using the foregoing slope-tangent method, one of the curves is
displaced
2o along the ordinate axis such that the curves coincide at the lower T~
temperature
value. The difference in y-axis intercepts at room temperature yields the
strain, ~,
expected if the glasses were not conjoined. The expected tensile stress, ~',
fox the
material showing the greater amount of contraction over the temperature range
from
T~ to room temperature, can be computed simply from the following equation:
6=E~E, (4)
where E is the elastic modulus for that material. Typically, residual stress
values less
than about 100 MPa (e.g., about 50 MPa or Less, about 30 MPa or less), are
sufficiently small to indicate that two materials are compatible.
A fourth selection criterion is to match the thermal stability of candidate
so materials. A measure of the thermal stability is given by the temperature
interval (Tx -
T~), where Tx is the temperature at the onset of the crystallization as a
material cools
37
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
slowly enough that each molecule can find its lowest energy state.
Accordingly, a
crystalline phase is a more energetically favorable state for a material than
a glassy
phase. However, a material's glassy phase typically has performance and/or
manufacturing advantages over the crystalline phase when it comes to fiber
s waveguide applications. The closer the crystallization temperature is to the
glass
transition temperature, the more likely the material is to crystallize during
drawing,
which can be detrimental to the fiber (e.g., by introducing optical
inhomogeneities
into the fiber, which can increase transmission losses). Usually a thermal
stability
interval, (Tx - T~) of at least about 80°C (e.g., at least about
100°C) is sufficient to
o permit fiberization of a material by drawing fiber from a preform. In
preferred
embodiments, the thermal stability interval is at least about 120°C,
such as about
150°C or more, such as about 200°C or more. Tx can be measured
using a thermal
analysis instrument, such as a differential thermal analyzer (DTA) or a
differential
scanning calorimeter (DSC).
1s A further consideration when selecting materials that can be co-drawn are
the
materials' melting temperatures, Tm. At the melting temperature, the viscosity
of the
material becomes too low to successfully maintain precise geometries during
the fiber
draw process. Accordingly, in preferred embodiments the melting temperature of
one
material is higher than the working temperature of a second, rheologically
compatible
2o material. In other words, when heating a preform, the preform reaches a
temperature
at it can be successfully drawn before either material in the preform melts.
One example of a pair of materials which can be co-drawn and which provide
a photonic crystal fiber waveguide with high index contrast between layers of
the
confinement region are As2Se3 and the polymer PES. As2Se3 has a glass
transition
25 temperature (T~) of about 180°C and a thermal expansion coefficient
(TEC) of about
24 x 10-x/°C. At 10.6 ~.m, AsZSe3 has a refractive index of 2.7775, as
measured by
Hartouni and coworkers and described in Proc. SP1E, 505, 11 (1984), and an
absorption coefficient, a, of 5.8 dB/m, as measured by Voigt and Linke and
described
in "Physics and Applications of Non-Crystalline Semiconductors in
Optoelectronics,"
3o Ed. A. Andriesh and M. Bertolotti, NATO ASI Series, 3. High Technology,
Vol. 36,
p. 155 (1996). Both of these references are hereby incorporated by reference
in their
38
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
entirety. PES has a TEC of about 55 x 10-x/°C and has a refractive
index of about
1.65.
Embodiments of photonic crystal fibers and methods for foaming photonic
crystal fibers are described in the following patents and patent applications:
U.S.
s Patent No. 6,625,364, entitled "LOW-LOSS PHOTONIC CRYSTAL WAVEGUIDE
.HAVING LARGE CORE RADIUS;" U.S. Patent No. 6,563,981, entitled
"ELECTROMAGNETIC MODE CONVERSION IN PHOTONIC CRYSTAL
MCTLTIMODE WAVEGUmES;" U.S. Patent Application Serial No. 10/057,440,
entitled "PHOTONIC CRYSTAL OPTICAL WAVEGUmES HAVING TAILORED
1 o DISPERSION PROFILES," and filed on January 25, 2002; U.S. Patent
Application
Serial No. 10/121,452, entitled "HIGH INDEX-CONTRAST FIBER WAVEGUIDES
AND APPLICATIONS," and filed on April 12, 2002; U.S. Patent No. 6,463,200,
entitled "OMNIDIRECTIONAL MULTILAYER DEVICE FOR ENHANCED
OPTICAL WAVEGU117ING;" Provisional 60/428,382, entitled "HIGH POWER
15 WAVEGUIDE," and filed on November 22, 2002; U.S. Patent Application Serial
No.
10/196,403, entitled "METHOD OF FORMING REFLECTING DIELECTRIC
MIRRORS," and filed on July 16, 2002; U.S. Patent Application Serial No.
10/720,606, entitled "DIELECTRIC WAVEGUIDE AND METHOD OF MAKING
THE SAME," and filed on November 24, 2003; U.S. Patent Application Serial No.
20 10/733,873, entitled "FIBER WAVEGUIDES AND METHODS OF MAKING
SAME," and filed on December 10, 2003. The contents of each of the above
mentioned patents and patent applications are hereby incorporated by reference
in
their entirety.
Referring again to FIG. 1, in some embodiments, photonic crystal fiber 120
2s can be can be designed so that the fiber bends preferably in a certain
plane. For
example, referring to FIG. 3, a photonic crystal fiber 300 includes a cladding
360 that
has an asymmetric cross-section with a larger diameter along a major axis 361
compared to its diameter along a minor axis 362 orthogonal to the major axis.
The
major and minor axes are orthogonal to axis 399. The asymmetric cross-section
is
so also manifested in the shape of the cladding's outer surface, which
includes portions
of differing curvature. In particular, cladding 360 includes arcuate portions
331 and
332 and two straight portions 333 and 334. Arcuate portions 331 and 332 are on
39
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
opposite sides of the cladding along major axis 321. Straight portions 333 and
334
axe on opposite sides of the cladding along minor axis 322.
In general, the asymmetry of the cross-sectional profile of cladding 360 is
sufficient to cause fiber 300 to preferably bend in a plane defined by fiber
axis 399
and the minor axis 362 during normal use of the fiber.
The ratio of fiber 300's diameter along the major axis to its diameter along
the
minor axis can vary. Typically, this ration is selected so that fiber 300
bends
preferably in the bend plane, while cladding 300 still provides the desired
mechanical
support or other functions) for which it is designed (e.g., optical function,
thermal
1 o management). In some embodiments, this ratio can be relatively low, such
as about
1.5:1 or less (e.g., about 1.3:1 or less, about 1.1:1 or less). Alternatively,
in certain
embodiments, this ratio can be larger than about 1.5:1 (e.g., about 1.8:1 or
more,
about 2:1 or more).
Photonic crystal fiber 300 also includes a core 320 and a confinement region
15 310 that includes spiral layers 330, 340, and 350, and has an inner seam
321 and an
outer seam 322 corresponding to the edges of the continuous layers from which
the
confinement region is formed. Inner seam 321 is located along an azimuth 323
that is
displaced by an angle cc from minor axis 362. a can be about 10° or
more (e.g., about
20° or more, about 30° or more, about 40° or more, about
50° or more, about 60° or
2o more, about 70° or more, about 80° or more). In some
embodiments, a, is about 90°.
The inner seam does not lie in the preferred bending plane of the fiber. In
fiber 300, this is achieved by locating inner seam 321 away from the minor
axis.
Locating the inner seam away from the preferred bending plane can be
advantageous
since it is believed that losses (e.g., due to scattering and/or absorption)
of guided
zs radiation is higher at the seam compared to other portions of the
confinement region.
Further, it is believed that the energy density of guided radiation in the
core is higher
towards the outside of a bend in the fiber relative to the energy density at
other parts
of the core. By locating the inner seam relative to the minor axis so that the
seam is
unlikely to lie in the preferred bending plane (e.g., where a, is about
90°), the
3o probability that the inner seam will lie towards the outside of a fiber
bend is reduced.
Accordingly, the compounding effect of having a relatively high loss portion
of the
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
confinement region at the region where the energy density of guided radiation
is high
can be avoided, reducing the loss associated with bends in the fiber.
Although inner seam 321 and outer seam 322 are positioned at the same
azimuthal position with respect to axis 399 in fiber 300, in other embodiments
the
inner and outer seams can be located along at different relative azimuthal
positions
with respect to the fiber's axis.
As discussed previously, the cladding provides mechanical support for the
fiber's confinement region. Accordingly, the thickness of cladding 360 can
vary as
desired along major axis 361. The thickness of cladding 360 along minor axis
362
~o can also vary but is generally less than the thickness along the major
axis. In some
embodiments, cladding 360 is substantially thicker along the major axis than
confinement region 310. For example, cladding 360 can be about 10 or more
times
thicker than confinement region 310 (e.g., more than about 20, more than about
30,
more than about 50 times thicker) along the major axis.
Fiber asymmetry can be introduced by shaving the perform, and then drawing
the fiber from the perform that has an asymmetric cross-section.
Alternatively, in
some embodiments, the fiber asymmetry can be introduced after the fiber is
drawn
from a perform. For example, a fiber can be shaved or ground as part of the
production process after being drawn but before being spooled.
2o Although fiber 300 includes a confinement region that has a seam, in
general,
embodiments of asymmetric fibers can include confinement regions with no seams
(e.g., confinement regions that are formed from a number of annular layers).
Furthermore, while fiber 300 has a shape composed of two circular arcs and
two straight lines, in general, fibers can have other shapes. For example,
fibers can
have asymmetric polygonal shapes, can be formed from arcuate portions having
different radii of curvature, and/or from arcuate portions that curve in
opposite
directions. Generally, the shape should provide the fiber with a preferred
bending
plane.
While the foregoing fibers are asymmetric with respect to their cross-
sectional
so shape, in general, fibers can be asymmetric in a variety of ways in order
to provide a
preferred bend plane. For example, in some embodiments, fibers can include
material
asymmetries that give rise to a preferred bend plane. Material asymmetries
refer to
41
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
variations between the material properties of different portions of a fiber
that cause
the fiber to bend preferably in a particular way. For example, a portion of a
fiber
cladding can be formed from a material that is mechanically less rigid that
other
portions, causing the fiber to bend preferably at that portion. Mechanical
variations
s can be caused by compositional changes or by physical differences in
portions having
the same composition. Compositional differences can be introduced, e.g., by
doping
portions of a fiber or fiber preform with a dopant that alters the mechanical
properties
of a fiber. As another example, compositional differences can be introduced by
forming different portions of a fiber from different compounds. Physical
differences
1 o refer to, e.g., differences in the degree of crystallinity in different
portions of a fiber.
Physical differences, such as differences in crystallinity, can be introduced
by
selectively heating and/or cooling portions of a fiber during fiber
fabrication, and/or
using different rates of heating/cooling on different fiber portions.
Furthermore, in some embodiments, fibers can include a symmetric first
cladding, but can include additional structure outside of the cladding that
cause the
fiber to bend preferably in a particular plane. For example, fibers can be
placed in
one or more sheaths that are asymmetric when it comes to allowing the fiber to
bend.
Referring again to FIG. 1, laser system 100 also includes a cooling apparatus
170, which delivers a cooling fluid (e.g., a gas or a liquid) to fiber 120 via
a delivery
2o tube 171 and coupling assembly 130. The cooling fluid is pumped through the
core
and absorbs heat from the fiber surface adjacent the core. In the present
embodiment,
the cooling fluid flows in the same direction as the radiation from laser 110,
however,
in some embodiments, the cooling fluid can be pumped counter to the direction
of
propagation of the laser radiation.
25 The flow rate of the cooling fluid through the core of photonic crystal
fiber
120 can vary as desired. Typically, the flow rate depends on the operating
power of
the laser, the absorption of the fiber at the operating wavelength, the length
of the
fiber, and the size of the fiber core, for example. Generally, the flow rate
should be
sufficient to cool the fiber at its operating power. In some embodiments, the
flow rate
3o can be about 0.1 liters/min or more (e.g., about 0.5 liters/min or more,
about 1
liter/min or more, about 2 liters/min or more, about 5 liters/min or more,
about 8
liters/min or more, about 9 liters/min or more, about 10 liters/min or more).
42
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
The pressure of cooling fluid exhausted from the fiber can vary. In some
embodiments, the pressure of the cooling fluid can be relatively high. For
example,
where the fluid exits from the same end of the fiber as the radiation, a
cooling gas can
be at sufficiently high pressure to clear debris from the target tissue of the
patient.
The gas pressure can be about 0.2 PSI or more (e.g., about 0.5 PSI or more,
about 1
PSI or more). In some embodiments, the pressure of a gas exiting the core of a
fiber
can correspond to a flow rate of about 1 liter/min or more (e.g., about 2
liter/min or
more, about 5 liter/min or more, about 8 liter/min or more, about 10 liter/min
or more)
through a 1 meter length of fiber having a core diameter of about 500 ~,m.
1 o The flow rate can be nominally constant while the system is activated, or
can
vary depending on the state operation of the laser system. For example, in
some
embodiments, the flow rate can be adjusted based on whether radiation is being
directed through fiber 120 or not. At times where the laser is activated and
radiation
is directed through the fiber, the flow rate can be at a level sufficient to
adequately
1 s cool the fiber. However, between radiation doses, the system can reduce
the flow rate
to a lower level (e.g., about 10% or less than the rate used to cool the fiber
while the
laser is activated). The gas flow rate can be triggered using remote control
152 or an
additional remote control that the operator can easily operate while using the
system.
In general, the temperature of the cooling fluid directed to the fiber can
vary.
2o In some embodiments, the cooling fluid is directed to the fiber at ambient
temperature
(e.g., at room temperature). In certain embodiments, the cooling fluid is
cooled below
ambient temperature prior to cooling the fiber. The cooling fluid can be
cooled so
that fluid exhausted from the fiber is within a certain temperature range. For
example,
the cooling fluid can be sufficiently cooled so that fluid exhausted from the
fiber does
2s not scald the patient if it comes into contact with the patient. As another
example, the
cooling fluid can be sufficiently cooled so that fluid exhausted from the
fiber is
between room temperature and body temperature. In some embodiments, the
cooling
fluid directed to the fiber can be cooled so that it has a temperature below
room
temperature. For example, the fluid can have a temperature of about
20°C or less
30 (e.g., , about 10°C or less, about 0°C or less, about -
10°C or less, about -20°C or less,
about -50°C or less).
43
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
In certain embodiments, where the cooling fluid flows through the fiber core
in the laser radiation propagation direction, it can perform additional
functions where
it impinges on the target tissue of the patient. For example, in some
embodiments,
heated fluid (e.g., gas) exiting the fiber can reduce bleeding at incised
blood vessels
s (or other tissue) by enhancing coagulation of the blood. It is believed that
coagulation
of blood is accelerated at temperatures of about 60°C or more.
Accordingly, where
the gas exiting the fiber impinging the target tissue is about 60°C or
more, it can
increase the rate at which blood coagulates, which can assist the surgeon by
reducing
the need to suction blood from the operating area. In some embodiments, the
1 o temperature of gas exiting the fiber can be, for example, about
50°C or more, about
60°C or more, about 65°C or more, about 70°C or more,
about 80°C or more, about
90°C or more, about I00°C or more). Alternatively, in certain
embodiments, the
temperature of the gas exiting the fiber can be below room temperature (e.g.,
about
10°C or less, about 0°C or less). For example, the system can
provide cooled gas to
15 the target location in procedures where it is beneficial to cool tissue
before irradiating
the tissue. In certain embodiments, the temperature of gas exiting the fiber
can be
approximately at body temperature (e.g., at about 37°C),
Gas flowing through the fiber core can be heated by about 5-
10°C/Watt of
input power (e.g., about 7-8°C/Watt). For example, a fiber having an
input power of
2o about 20 Watts could heat gas flowing through its core by about 100-
200°C.
In some embodiments, the fluid flowing through the fiber's core can be used
to deliver other substances to the target tissue. For example, atomized
pharmaceutical
compounds could be introduced into a gas that is flowed through the core and
delivered via the photonic crystal fiber to the target tissue.
2s In general, the type of cooling fluid can vary as desired. The cooling
fluid can
be liquid, gas, or superfluid. In some embodiments, the cooling fluid includes
a noble
gas (e.g., helium, neon, argon, krypton, and/or xenon), oxygen, carbon
dioxide, and/or
nitrogen. The cooling fluid can be composed substantially of a single compound
(e.g., having a purity of about 98% or more, about 99% or more, about 99.5% or
so more, about 99.8°70 or more, about 99.9% or more), or can be a
mixture (e.g., air or
heliox).
44
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
In some embodiments, the cooling fluid is selected based on its ability to
cool
the fiber. The cooling ability of a fluid can depend on the fluids flow rate
and/or the
fluids thermal conductivity. Helium gas, for example, has a relatively high
thermal
conductivity compared to other gases. Furthermore, for a given pressure drop,
helium
s can have a higher flow rate than other gases, such as nitrogen. Accordingly,
in some
embodiments, helium can be selected based on its ability to cool the fiber
better than
other gases.
Alternatively, or additionally, the cooling fluid can be selected based on
whether or not it has any adverse interactions with the patient. For example,
in
1 o embodiments where the cooling fluid is in close proximity to the patient,
it can be
selected based on its relatively low toxicity. In certain embodiments, a
cooling fluid
can be selected based on its solubility compared to other fluids. A fluid with
relatively low solubility in blood can reduce the risk of the patient having
an
embolism due to exposure to the cooling fluid. An example of a fluid with
relatively
15 low toxicity and relatively low solubility is helium gas.
The cooling fluid can also be selected based on other criteria, such as its
reactivity with other elements (e.g., flammability). In some embodiments, a
cooling
fluid, such as helium, can be selected based on its inert characteristics
(e.g.,
inflammability).
2o In certain embodiments, a protective sleeve can be attached to the output
end
of photonic crystal fiber 120. Sleeves can be used to prevent debris buildup
and
clogging of the fiber's output end. An example of a sleeve 401 is shown in
FIG. 4A.
Sleeve 401 is attached to the output end of a photonic crystal fiber 410.
Sleeve 401
includes a collar 425 that maintains a stand off distance 405 between the
output end of
25 the fiber and a distal opening 430 of the sleeve. Typically, stand off
distance 405 is
from about 0.5 cm to about 4 cm long. Radiation 411 exiting core 420 of fiber
410
exits the sleeve through distal opening 430.
Sleeve 401 can also include perforations to reduce the pressure of fluid
exiting
the fiber at distal opening 430. For example, sleeve 401 includes secondary
openings
30 435 and 436 that, along with distal opening 430, provide paths through
which fluid
exiting core 420 can exit the sleeve.
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
Typically, sleeves are formed from rigid materials that can be readily
sterilized. For example, sleeves can be formed from stainless steel. Sleeves
can be
disposable or reusable.
Another example of a sleeve is sleeve 401A shown in FIG. 4B. Sleeve 401A
s narrows along its length, having a larger diameter 402B where it attaches to
the output
end of fiber 401 compared to the diameter 402A near the distal opening. The
narrowing sleeve increases the pressure of fluid from core 420 in the sleeve,
increasing the fluid pressure at openings 435A and 435B, thereby reducing the
possibility of debris being sucked into the sleeve through these openings.
1 o In some embodiments, sleeves can include one or more optical components.
For example, referring to FIG. 4C, a sleeve 401B can include a reflector 440
(e.g., a
mirror) attached near the distal opening. Reflector 440 redirects radiation
4I1 exiting
core 420, and can enable an operator to direct the radiation into confined
spaces not
otherwise accessible.
15 In embodiments, sleeves can also include transmissive optical components.
For example, referring to FIG. 4D, a sleeve 4010 includes a lens 450 mounted
near
distal opening 430. Lens is mounted within the sleeve by a lens mount 451,
which is
positioned between distal opening 430 and secondary openings 435 and 436 so
that
fluid from the fiber can still exit sleeve 401C through openings 435 and 436.
Lens
20 450 focuses radiation 411 exiting core 420 to a waist at some position
beyond distal
opening 430. Another example of a transmissive optical component that can be
mounted within a sleeve is a transmissive optical flats, which can serve as a
window
for the transmission of radiation exiting the fiber core while preventing
fluid flow
through distal opening 430.
2s As discussed previously, in laser system 100, light is coupled from laser
110
and fluid from fluid source 170 into fiber 120 by coupling assembly 130.
Refernng to
FIG. 5A, an example of a coupler for coupling gas and radiation into a
photonic
crystal fiber is coupling assembly 500. Coupling assembly 500 includes a first
portion 510 that receives radiation from the laser and gas from a gas source,
and a
3o second portion 520 that connects to photonic crystal fiber 120. First
portion 510 is
coupled to second portion 520 by a flexible junction 505 (e.g., a metallic
bellows or
rubber tube).
46
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
First portion 510 includes a lens holder 502 and an adaptor 504 for the lens
holder. The lens holder can be a commercially available lens holder. When
coupled
to lens holder 5-2, adaptor 504 secures a lens 501 in the lens holder. An o-
ring 503
creates a seal between adaptor 504 and lens 501. Adaptor 504 also includes a
fitting
s 504a for connecting to tube that supplies gas to the system. In some
embodiments,
fitting 504a includes a barbed hose fitting.
Portion 520 includes a connector alignment stage 508 including a fiber optic
connector receptacle (e.g., a commercially available stage, such as component
LP-lA,
available from Newport (Irvine, CA)). Stage 508 is connected to flexible
junction
505 by an adaptor 506. An o-ring 507 creates a seal between stage 508 and
adaptor
506. A fiber optic connector 509 couples photonic crystal fiber 510 to stage
58.
Another o-ring 5I I creates a seal between fiber optic connector 509 and stage
508.
Another example of a coupling assembly is shown in FIG. 5B. Coupling
assembly 530 includes a laser connector 540 that attaches to the output
terminal 111
of laser 110. Coupling assembly 530 includes a housing 531 attached to laser
connector 540. The housing includes a fluid inlet port 533 and a radiation
output port
534. A fiber optic connector 550 affixes to radiation output port 534,
positioning an
end of a photonic crystal fiber 551 relative to the radiation output port. In
addition, a
connector 560 connects a fluid conduit 561 to the housing by attaching to
fluid input
2o port 533.
A retardation reflector 532 is positioned within housing 531. Retardation
reflector 532 directs linearly polarized radiation 541 entering the housing
from the
laser towards a radiation output terminal 534, modifying the polarization
state so that
reflected radiation 542 is circularly polarized. More generally, the
reflective retarder
2s modifies the polarization state of the laser radiation to provide a lower
loss
polarization to fiber 551. In embodiments, average losses of circularly
polarized
radiation may be lower than linearly polarized radiation where the fiber has
high loss
regions that may be coincident with the plane of polarization. For example,
photonic
crystal fibers that have a confinement region having a seam can exhibit higher
losses
so for radiation polarized in the plane of the seam compared to circularly
polarized light.
Alternatively, or additionally to having a retarder, fiber 551 can be attached
with its
47
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
seam (or other high loss region) in a particular orientation with respect to
the
polarization state of radiation from the laser.
Examples of a reflective retarder suitable for 10.6 micron radiation are
series
PRR: Silicon & Copper Phase Retardation Reflectors (commercially-available
from
s Laser Research Optics (Providence, RI). Transmissive retarders (e.g., formed
from
birefringent crystals) can be used in place of, or in addition to, retardation
reflector
532.
Coupling assembly 530 also includes a lens 545, mounted within housing 531
by mount 535, which focuses reflected radiation 542 to a waist at radiation
output port
534 where it couples into the core of fiber 551. Lenses suitable for use at
10.6 micron
wavelengths, for example, can be formed from ZnSe.
In embodiments where cooling fluid is not coupled into the fiber's core, other
coupling assemblies can be used. Generally, in such embodiments, any coupler
suitable for the wavelength and intensity at which the laser system operates
can be
used. One type of a coupler is described by R. Nubling and J. Harrington in
"Hollow-
waveguide delivery systems for high-power, industrial C02 lasers," Applied
Optics,
34, No. 3, pp. 372-380 (1996). Other examples of couplers include one or more
focusing elements, such as one or more lenses. More generally, the coupler can
include additional optical components, such as beam shaping optics, beam
filters and
2o the like.
In general, coupling efficiency can be relatively high. For example, coupling
assembly 130 can couple more than about 70% of the laser output at the guided
wavelength into a guided mode in the fiber (e.g., about 80% or more, 90% or
more,
95% or more, 98% or more). Coupling efficiency refers to the ratio of power
guided
2s away by the desired mode to the total power incident on the fiber.
While laser system 100 includes handpiece 140, systems can include different
types of handpieces depending on the medical application for which they are
being
used. In general, a handpiece includes a portion that the operator can grip,
e.g., in
his/her palm or fingertips, and can include other components as well. In
certain
3o embodiments, handpieces can include endoscopes (e.g., flexible or rigid
endoscopes),
such as a cystoscopes {for investigating a patient's bladder), nephroscopes
(for
investigating a patient's kidney), bronchoscopes (for investigating a
patient's
48
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
bronchi), laryngoscopes (for investigating a patient's larynx), otoscopes (for
investigating a patient's ear), arthroscopes (for investigating a patient's
joint),
laparoscopes (for investigating a patient's abdomen), and gastrointestinal
endoscopes.
Another example of a handpiece is a catheter, which allows an operator to
position the
output end of the photonic crystal fiber into canals, vessels, passageways,
and/or body
cavities.
Moreover, handpieces can be used in conjunction with other components,
without the other component being integrated into the handpiece. For example,
handpieces can be used in conjunction with a trocar to position the output end
of a
1 o photonic crystal fiber within an abdominal cavity of a patient. In another
example, a
handpiece can be used in conjunction with a rigid endoscope, where the rigid
endoscope is not attached to the gripping portion of the handpiece or to the
photonic
crystal fiber.
Referring to FIG. 6, in some embodiments, a handpiece 680 includes a narrow
conduit 684 that includes a channel through which photonic crystal fiber 120
is
inserted. Conduit 684 can be made from a rigid, but deformable, material
(e.g.,
stainless steel). This allows the operator to bend the conduit (e.g., by hand
or using a
tool) to a desired amount (e.g., such as at bend 686) for a procedure, where
the
conduit retains the bend until the operator straightens it or bends it in a
different way.
2o Handpiece 680 also includes a gripping portion 682 attached to conduit 684,
which
allows the operator to comfortably hold the handpiece.
In certain embodiments, handpieces can include actuators that allow the
operator to bend the fiber remotely, e.g., during operation of the system. For
example, referring to FIG. 7A, in some embodiments, laser radiation 112 can be
2s delivered to target tissue 699 within a patient 601 using an endoscope 610.
Endoscope 610 includes a gripping portion 611 and a flexible conduit 615
connected
to each other by an endoscope body 616. An imaging cable 622 housing a bundle
of
optical fibers is threaded through a channel in gripping portion 611 and
flexible
conduit 615. Imaging cable 622 provide illumination to target tissue 699 via
flexible
3o conduit 615. The imaging cable also guides light reflected from the target
tissue to a
controller 620, where it is imaged and displayed providing visual information
to the
49
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
operator. Alternatively, or additionally, the endoscope can include an
eyepiece lens
that allows the operator to view the target area directly through the imaging
cable.
Endoscope 610 also includes an actuator 640 that allows the operator to bend
or straighten flexible conduit 615. In some embodiments, actuator 640 allows
flexible
s conduit 615 to bend in one plane only. Alternatively, in certain
embodiments, the
actuator allow the flexible conduit to bend in more than one plane.
Endoscope 610 further includes an auxiliary conduit 630 (e.g., a detachable
conduit) that includes a channel through which fiber 120 is threaded. The
channel
connects to a second channel in flexible conduit 615, allowing fiber 120 to be
1 o threaded through the auxiliary conduit into flexible conduit 615. Fiber
120 is attached
to auxiliary conduit in a matter than maintains the orientation of the fiber
with respect
the channel through flexible conduit 615, thereby minimizing twisting of the
photonic
crystal fiber about its waveguide axis within the flexible conduit. In
embodiments
where photonic crystal fiber 120 has a confinement region that includes a
seam, the
15 fiber can be attached to the auxiliary conduit so that the seam is not
coincident with a
bend plane of the flexible conduit.
In general, photonic crystal fibers can be used in conjunction with
commercially-available endoscopes, such as endoscopes available from PENTAX
Medical Company (Montvale, NJ) and Olympus Surgical & Industrial America, Inc.
20 (Orangeburg, NY).
Auxiliary conduit 630 can be configured to allow the user to extend and/or
retract the output end of the photonic crystal fiber within flexible conduit
615. For
example, referring to FIG. 7B, in some embodiments, auxiliary conduit 630 of
endoscope 610 can include two portions 631 and 632 that are moveable with
respect
25 to each other. Portion 632 is attached to endoscope body 616, while portion
631
telescopes with respect to portion 632. Portion 632 includes a connector 636
that
connects to a fiber connector 638 attached to fiber 120. The mating mechanism
of
connector 636 and fiber connector 638 can allow for quick and simple removal
and
attachment of the photonic crystal fiber to the endoscope. When attached,
connector
so 636 and fiber connector 638 substantially prevent fiber 120 from twisting,
maintaining its orientation about the fiber axis within flexible conduit 615.
The
connectors can maintain the orientation of the fiber in the conduit with a
seam in the
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
fiber oriented away from a bend plane of the conduit, for example.
Furthermore,
when portion 631 extends or retracts with respect to portion 632, it extends
or retracts
the output end 645 of fiber 120 with respect to the distal end 618 of flexible
conduit
615. Auxiliary conduit 630 also includes a locking mechanism 634 (e.g., a
latch or
clamp) that allows the user to lock the portion 631 with respect to portion
632. The
locking mechanism prevents unwanted movement of fiber 120 within flexible
conduit
615 while radiation is being delivered to the patient.
While laser systems 100 and 600 include a single length of a photonic crystal
fiber that delivers radiation from laser 110 to the target location, multiple
connected
i o lengths of photonic crystal fiber can also be used. For example, referring
to FIG. 7C,
a laser system 700 includes two lengths of photonic crystal fiber 720 and 721
rather
than a single length of photonic crystal fiber as laser systems 100 and 600.
Photonic
crystal fiber lengths 720 and 721 are coupled together by a connector 730 that
attaches to auxiliary conduit 630 of endoscope 610.
Laser system 700 includes a secondary cooling apparatus 740 in addition, or
alternatively, to cooling apparatus 170. Photonic crystal fiber length 720 is
placed
within a sheath 744, which is connected to secondary cooling apparatus 740 by
a
delivery tube 742. Secondary cooling apparatus 740 cools photonic crystal
fiber
length 720 by pumping a cooling fluid through sheath 744.
2o Secondary cooling apparatus 740 can recirculate the cooling fluid it pumps
through sheath 744. For example, sheath 744 can include an additional conduit
that
returns the cooling fluid to secondary cooling apparatus 740. A heat exchanger
provided with the secondary cooling system can actively cool the exhausted
cooling
fluid before the secondary cooling system pumps the fluid back to sheath 744.
The cooling fluid can be the same or different as the cooling fluid pumped
into
the core of the photonic crystal fiber by cooling apparatus 170. In some
embodiments, cooling apparatus 170 pumps a gas through the core of the fiber,
while
secondary cooling apparatus 740 cools the fiber using a liquid (e.g., water).
Sheath 744 can perform a protective function, shielding photonic crystal fiber
ao length 720 from environmental hazards. In some embodiments, sheath 744
includes a
relatively rigid material (e.g., so that sheath 744 is more rigid than
photonic crystal
fiber length 720), reducing flexing of photonic crystal fiber length 720. In
some
51
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
embodiments, sheath 744 is formed from a relatively rigid material, such as
nitinol
(commercially-available from Memry, Inc., Bethel, CT).
In embodiments, using two lengths of photonic crystal fiber can prolong the
usable lifetime of at least one of the lengths. For example, due to the
additional
cooling and/or protection afforded the fiber length by cooling apparatus 740
and/or
sheath 744, photonic crystal fiber length 720 can be replaced less often than
fiber
length 721. In some embodiments, fiber length 721 can be used multiple times,
while
fiber length 721 is discarded after each use.
While laser system 700 utilizes two connected lengths of photonic crystal
1o fiber, more generally, waveguides other than photonic crystal waveguides
can also be
connected to a length of photonic crystal fiber to provide a conduit for
delivering
radiation from a laser to the target location. For example, a length of a
hollow
metallic waveguide can be connected to a length of a photonic crystal fiber to
provide
a conduit for IR radiation.
Furthermore, in general, other conduits can be bundled with photonic crystal
fibers in a medical laser system to, e.g., deliver something to, remove
something
from, or to observe the target tissue during the procedure. For example, as
discussed
in reference to FIG. 7A, the photonic crystal fiber can be bundled with other
optical
waveguides, such as an imaging cable used to illuminate and/or image the
target
2o tissue using an imaging system. In certain embodiments, laser systems can
deliver
radiation from more than one radiation source to the patient by delivering
radiation
from a laser radiation through the photonic crystal fiber, and radiation from
a second
source (e.g., a second laser) through the other conduit (e.g., an optical
fiber). As an
example, referring to FIG. 8, in certain embodiments, a system 800 includes a
fiber
waveguide 830 and a photonic crystal fiber 810, with a portion of fiber
waveguide
830 and photonic crystal fiber 810 being bundled within a jacket 850 (e.g., a
flexible
jacket, such as a flexible polymer jacket). Photonic crystal fiber 810 is
coupled to a
laser 820, which delivers radiation at wavelength ~,1 through the core 812 of
photonic
crystal fiber 810. Fiber waveguide 830 is coupled to another radiation source
840,
which delivers radiation at a different wavelength, ~,2, through the core 832
of fiber
waveguide 830. Photonic crystal fiber 810 and fiber waveguide 830 deliver
radiation
52
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
(indicated by reference numerals 822 and 842, respectively) at wavelengths ~.1
and ~,Z,
respectively, to a common location.
Fiber waveguide 830 can be, for example, an optical fiber or a photonic
crystal
fiber. Radiation source 840 can be a laser or other light source (e.g., a bulb
or light
emitting diode). As an example, in some embodiments, radiation source 840 is a
Iaser
that emits visible radiation (e.g., ~,2 is within a range from about 400 nm to
about 800
nm, such as 633 nm), such as a I3eNe laser and fiber waveguide 830 is an
optical
fiber. The visible radiation emitted from fiber 830 allows the operator to aim
the
output end of the photonic crystal fiber to the appropriate tissue before
delivering
laser radiation from laser 820. In another example, the other radiation source
840 is
an Nd:YAG laser, which can also be used to deliver radiation to the patient
for
photocoagulation or photoablation purposes.
Jacket 850 can have a sufficiently small outer diameter to allow the jacket to
be used in conjunction with a variety of handpieces. For example, the jacket
can have
an outer diameter of about 2 mm or less, allowing the jacket to be inserted
into a
standard-size channel of an endoscope.
In some embodiments, the photonic crystal fiber can be bundled with a tube
for delivering gas to (e.g., hot gas for blood coagulation) or vacuuming
debris at the
target location, as an alternative or in addition to being bundled with a
fiber
2o waveguide.
Fox example, referring to FIG. 9, a system 900 a photonic crystal fiber 910 is
bundled with a tube 930 for exhausting fluid (e.g., cooling fluid) exiting the
photonic
crystal fiber's core 912 at the fiber's output end. The system shown in FIG. 9
includes a laser 920 and a fluid source 926 that deliver radiation and fluid
to the
2s photonic crystal fiber's core 912 via a coupling assembly 924. The system
also
includes a pump that draws fluid exiting core 912 through tube 930 away from
the
patient.
The output end of fiber 910 and input end of tube 930 are coupled together by
a cap 960, that fits over the ends of the fiber and tube. Cap 960 includes a
window
30 962 that is made from a material substantially transparent to the
wavelength of
radiation being delivered from laser 920. Cap 960 positions window 962 in the
path
53
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
of radiation 922 exiting core 912, allowing the system to deliver the
radiation to the
patient. Fluid exiting core 912, however, is drawn through an exhaust port 964
into
tube 942. Pump 940, connected to the opposite end of tube 930, draws the fluid
942
through the tube away from the patient.
s A portion of tube 930 and photonic crystal fiber 910 are bundled together
within a jacket 950, providing a flexible duct that can be threaded through a
channel
in a handpiece (e.g., a handpiece including an endoscope).
System 900 can be used in procedures where it is undesirable to exhaust fluid
(e.g., cooling fluid) to the tissue being exposed to radiation. For example,
where the
1 o radiation is being delivered internally, where the exhausted fluid is
toxic, or is at an
undesirable temperature (e.g., sufficiently hot to burn the exposed tissue),
an exhaust
tube can be included with the photonic crystal fiber to prevent exposure of
the tissue
to the fluid.
In some cases, the handpiece in a medical laser system can be replaced by a
15 robot, which can be operated remotely. For example, robot-performed surgery
is
under consideration in applications where a surgeon cannot easily or rapidly
reach a
patient (e.g., a wounded soldier on a battlefield).
Since photonic crystal fibers are used in medical procedures, they should be
sterilizable. For example, photonic crystal fibers should be able to withstand
2o sterilizing procedures, such as autoclaving. Typically, lengths of photonic
crystal
fiber are provided to the user pre-sterilized and sealed in a container (e.g.,
vacuum
sealed in a container that has sufficient barrier properties to prevent
contamination of
the fiber length during storage and shipping). For example, sterilized lengths
of
photonic crystal fiber (e.g., about 0.5 meters to about 2.5 meters lengths)
can be
25 provided sealed (e.g., vacuum sealed) in a plastic container (e.g.,
including a barrier
film layer).
In general, the laser systems described above can be used in a number of
different medical applications. Generally, the type of laser, wavelength,
fiber length,
fiber outer diameter, and fiber inner diameter, among other system parameters,
will be
3o selected according to the application. Medical applications include
aesthetic medical
procedures, surgical medical procedures, ophthalmic procedures, veterinary
procedures, and dental procedures.
54
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
Aesthetic procedures include treatment for: hair removal; pulsed light skin
treatments for reducing fine wrinkle lines, sun damage, age spots, freckles,
some
birthmarks, rosacea, irregular pigmentation, broken capillaries, benign brown
pigment
and pigmentation; skin resurfacing; leg veins; vascular lesions; pigmented
lesions;
s acne; psoriasis & vitiligo; and/or cosmetic repigmentation.
Surgical procedures include procedures for gynecology, laparoscopy,
condylomas and lesions of the external genitalia, and/or leukoplakia. Surgical
applications can also include ear/noselthroat (ENT) procedures, such as laser
assisted
uvula palatoplasty (LAUD) (i.e., to stop snoring); procedures to remove nasal
obstruction; stapedotomy; tracheobronchial endoscopy; tonsil ablation; and/or
removal of benign laryngeal lesions. Surgical applications can also include
breast
biopsy, cytoreduction for metastatic disease, treatment of decubitus or statis
ulcers,
hemorrhoidectomy, laparoscopic surgery, mastectomy, and/or reduction
mammoplasty. Surgical procedures can also include procedures in the field of
1 s podiatry, such as treatment of neuromas, periungual, subungual and plantar
warts,
porokeratoma ablation, and/or radical nail excision. Other fields of surgery
in which
lasers may be used include orthopedics, urology, gastroenterology, and
thoracic ~
pulmonary surgery.
Ophthalmic uses include treatment of glaucoma, age-related macular
2o degeneration (AlViD), proliferative diabetic retinopathy, retinopathy of
prematurity,
retinal tear and detachment, retinal vein occlusion, and/or refractive surgery
treatment
to reduce or eliminate refractive errors.
Veterinary uses include both small animal and large animal procedures.
Examples of dental applications include hard tissue, soft tissue, and
2s endodontic procedures. Hard tissue dental procedures include caries removal
& cavity
preparation and laser etching. Soft tissue dental procedures include incision,
excision
& vaporization, treatment of gummy smile, coagulation (hemostasis), exposure
of
unerupted teeth, aphthous ulcers, gingivoplasty, gingivectomy, gingival
troughing for
crown impressions, implant exposure, frenectomy, flap surgery, fibroma
removal,
so operculectomy, incision & drainage of abscesses, oral papilectomy,
reduction of
gingival hypertrophy, pre-prosthetic surgery, pericoronitis, peri implantitis,
oral
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
lesions, and sulcular debridement. Endodontic procedures include pulpotomy,
root
canal debridement, and cleaning. Dental procedures also include tooth
whitening.
Generally, the type of laser, wavelength, fiber length, fiber outer diameter,
and
fiber inner diameter, among other system parameters, are selected according to
the
application. For example, embodiments in which the laser is a CO~ laser, the
laser
system can be used for surgical procedures requiring the ablation,
vaporization,
excision, incision, and coagulation of soft tissue. C02 laser systems can be
used for
surgical applications in a variety of medical specialties including aesthetic
specialties
(e.g., dermatology and/or plastic surgery), podiatry, otolaryngology (e.g.,
ENT),
1o gynecology (including laparoscopy), neurosurgery, orthopedics (e.g., soft
tissue
orthopedics), arthroscopy (e.g., knee arthroscopy), general and thoracic
surgery
(including open surgery and endoscopic surgery), dental and oral surgery,
ophthalmology, genitourinary surgery, and veterinary surgery.
In some embodiments, C02 laser systems can be used in the ablation,
15 vaporization, excision, incision, and/or coagulation of tissue (e.g., soft
tissue) in
dermatology and/or plastic surgery in the performance of laser skin
resurfacing, laser
dean-abrasion, and/or laser burn debridernent. Laser skin resurfacing (e.g,.
by
ablation and/or vaporization) can be performed, for example, in the treatment
of
wrinkles, rhytids, and/or furrows (including fine lines and texture
irregularities).
2o Laser skin resurfacing can be performed for the reduction, removal, and/or
treatment
of: keratoses (including actinic keratosis), seborrhoecae vulgares, seborrheic
wart,
and/or verruca seborrheica; vermillionectomy of the lip; cutaneous horns;
solar/actinic
elastosis; cheilitis (including actinic cheilitis); lentigines (including
lentigo maligna or
Hutchinson's malignant freckle); uneven pigmentation/dyschromia; acne scars;
25 surgical scars; keloids (including acne keloidalis nuchae); hemangiomas
(including
Buccal, port wine and/or pyogenic granulomas/granuloma pyogenicum/granuloma
telagiectaticum); tattoos; telangiectasia; removal of skin tumors (including
periungual
and/or subungual fibromas); superficial pigmented lesions; adenosebaceous
hypertrophy and/or sebaceous hyperplasia; rhinophyma reduction; cutaneous
so papilloma; milia; debridement of eczematous and/or infected skin; basal and
squamous cel carcinoma (including keratoacanthomas, Bowen's disease, and/or
Bowenoid Papulosis lesions); nevi (including spider, epidermal, and/or
protruding);
56
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
neurofibromas; laser de-epithelialization; tricoepitheliomas; xanthelasma
palpebrarum; and/or syringoma. COZ laser systems can be used for laser
ablation,
vaporization and/or excision for complete and/or partial nail matrixectomy,
for
vaporization and/or coagulation of skin lesions (e.g., benign and/or
malignant,
vascular and/or avascular), and/or for Moh's surgery, for lipectomy. Further
examples include using laser system 1300 for laser incision and/or excision of
soft
tissue for the performance of upper and/or lower eyelid blepharoplasty, and/or
for the
creation of recipient sites for hair transplantation.
In certain embodiments, C02 laser systems is used in the laser ablation,
1 o vaporization, and/or excision of soft tissue during podiatry procedures
for the
reduction, removal, and/or treatment of: verrucae vulgares/plantar warts
(including
paronychial, periungual, and subungual warts); porokeratoma ablation; ingrown
nail
treatment; neuromas/fibromas (including Morton's neuroma); debridement of
ulcers;
and/or other soft tissue lesions. C02 laser systems can also be used for the
laser
ablation, vaporization, and/or excision in podiatry for complete and/or
partial
matrixectomy. '
COZ laser systems can be used for laser incision, excision, ablation, and/or
vaporization of soft tissue in otolaryngology for treatment of: choanal
atresia;
leukoplakia (including oral, larynx, uvula, palatal, upper lateral pharyngeal
tissue);
2o nasal obstruction; adult and/or juvenile papillomatosis polyps; polypectomy
of nose
and/or nasal passages; lymphangioma removal; removal of vocal cordlfold
nodules,
polyps and cysts; removal of recurrent papillomas in the oral cavity, nasal
cavity,
larynx, pharynx and trachea (including the uvula, palatal, upper lateral
pharyngeal
tissue, tongue and vocal cords); laser/tumor surgery in the larynx, pharynx,
nasal, ear
25 and oral structures and tissue; Zenker' diverticulum/pharynoesophageal
diverticulum
(e.g., endoscopic laser-assisted esophagodiverticulostomy); stenosis
(including
subglottic stenosis); tonsillectomy (including tonsillar cryptolysis,
neoplasma) and
tonsil ablation/tonsillotomy; pulmonary bronchial and tracheal lesion removal;
benign
and malignant nodules, tumors and fibromas (e.g., of the larynx, pharynx,
trachea,
3o tracheobronchial/endobronchial); benign and/or malignant lesions andlor
fibromas
(e.g., of the nose or nasal passages); benign and/or malignant tumors and/or
fibromas
(e.g., oral); stapedotomy/stapedectomy; acoustic neuroma in the ear;
superficial
57
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
lesions of the ear (including chondrodermatitis nondularis chronica
helices/Winkler's
disease); telangiectasia/hemangioma of larynx, pharynx, and/or trachea
(including
uvula, palatal, and/or upper lateral pharyngeal tissue); cordectomy, cordotomy
(e.g.,
for the treatment of vocal cord paralysis/vocal fold motion impairment),
and/or cordal
lesions of larynx, pharynx, and/or trachea; myringotomy/tympanostomy (e.g.,
tympanic membrane fenestration); uvulopalatoplasty (e.g., LAUP); turbinectomy
and/or turbinate reduction/ablation; septal spur ablation/reduction and/or
septoplasty;
partial glossectomy; tumor resection on oral, subfacial and/or neck tissues;
rhinophyma; verrucae vulgares; and/or gingivoplasty/gingivectomy.
1o In some embodiments, C02 laser systems can be used for the laser incision,
excision, ablation, and/or vaporization of soft tissue in gynecology for
treatment of:
conizaton of the cervix (including cervical intraepithelial neoplasia, vulvar
and/or
vaginal intraepithelial neoplasia); condyloma acuminata (including cervical,
genital,
vulvar, preineal, and/or Bowen's disease, and/or Bowenoid papulosa lesions);
15 leukoplakia (e.g., vulvar dystrophies); incision and drainage of
Bartholin's and/or
nubuthian cysts; herpes vaporization; urethral caruncle vaporization; cervical
dysplasia; benign and/or malignant tumors; and/or hemangiomas.
C02 laser systems can be used for the vaporization, incision, excision,
ablation
andlor coagulation of soft tissue in endoscopic and/or laparoscopic surgery,
including
2o gynecology laparoscopy, for treatment of: endometrial lesions (inclusing
ablation of
endometriosis); excisionllysis of adhesions; salpingostomy;
oophorectomy/ovariectomy; fimbroplasty; metroplasty; tubal microsurgery;
uterine
myomas and/or fibroids; ovarian fibromas and/or follicle cysts; uterosacral
ligament
ablation; and/or hysterectomy.
2s In certain embodiments, C02 laser systems are used for the laser incision,
excision, ablation, and/or vaporization of soft tissue in neurosurgery for the
treatment
of cranial conditions, including: posterior fossa tumors; peripheral
neurectomy;
benign and/or malignant tumors and/or cysts (e.g., gliomos, menigiomas,
acoustic
neuromas, lipomas, and/or large tumors); arteriovenous malformation; andlor
pituitary
3o gland tumors. In some embodiments, CO2 laser systems are used for the laser
incision, excision, ablation, and/or vaporization of soft tissue in
neurosurgery for the
treatment of spinal cord conditions, including: incision/excision and/or
vaporization
58
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
of benign and/or malignant tumors and/or cysts; intra- and/or extradural
lesions;
andlor laminectomy/laminotomy/microdisectomy.
C02 laser systems can be used for the incision, excision, and/or vaporization
of soft tissue in orthopedic surgery in applications that include arthroscopic
and/or
s general surgery. Arthroscopic applications include: menisectomy;
chondromalacia;
chondroplasty; ligament release (e.g., lateral ligament release); excision of
plica;
and/or partial synovectomy. General surgery applications include: debridement
of
traumatic wounds; debridement of decubitis and/or diabetic ulcers;
microsurgery;
artificial joint revision; and/or polymer (e.g., polymethylmethacrylate)
removal.
1o COZ laser systems can also be used for incision, excision, and/or
vaporization
of soft tissue in general and/or thoracic surgery, including endoscopic and/or
open
procedures. Such applications include: debridement of decubitus ulcers,
stasis,
diabetic and other ulcers; mastectomy; debridement of burns; rectal and/or
anal
hemorrhoidectomy; breast biopsy; reduction mammoplasty; cytoreduction for
1 s rnetastatic disease; laparotomy and/or laparoscopic applications;
mediastinal and/or
thoracic lesions and/or abnormalities; skin tag vaporization; atheroma; cysts
(including sebaceous cysts, pilar cysts, and/or mucous cysts of the lips);
pilonidal cyst
removal and/or repair; abscesses; and/or other soft tissue applications.
In certain embodiments, COZ laser systems can be used for the incision,
2o excision, and/or vaporization of soft tissue in dentistry and/or oral
surgery, including
for: gingivectomy; gingivoplasty; incisional and/or excisional biopsy;
treatment of
ulcerous lesions (including aphthous ulcers); incision of infection when used
with
antibiotic therapy; frenectomy; excision and/or ablation of benign and/or
malignant
lesions; homeostasis;operculectomy; crown lengthening; removal of soft tissue,
cysts,
2s and/or tumors; oral cavity tumors and/or hemangiomas; abscesses; extraction
site
hemostasis; salivary gland pathologies; preprosthetic gum preparation;
leukoplakia;
partial glossectomy; and/or periodontal gum resection.
In some embodiments, COZ Iaser systems can be used for incision, excision,
and/or vaporization of soft tissue in genitourinary procedures, including for:
benign
so and/or malignant lesions of external genitalia; condyloma; phimosis; and/or
erythroplasia.
59
CA 02561485 2006-09-28
WO 2005/096783 PCT/US2005/012047
EXAMPLE
Surgery was performed to remove portions of the larynx from a dog using a
C02 laser system operating at 10.6 microns. The photonic crystal fiber used in
this
procedure had a hollow core approximately 550 microns in diameter. The fiber
had
spiral confinement region that included a radial profile of approximately 20
PES/As2Se3 bilayers. The bilayer thickness was approximately 3 microns, with a
thickness ration of approximately 2 to 1 (PES to As2Se3). The fiber's cladding
was
formed from PES, and the fiber's OD was approximately 1500 microns. The fiber
was 1.5 m long.
A complete en bloc supraglottic laryngectomy was performed including a
cordectomy. The laser radiation was delivered using the photonic crystal fiber
with a
semi-rigid hand-piece. The hand-piece was inserted through a rigid
laryngoscope.
The input power into the fiber was approximately 20 Watts. The radiation power
exiting the fiber was approximately 7 Watts. Nitrogen was blown through the
fiber in
1s the same direction as the radiation. The nitrogen flow rate was
approximately 1
liter/min.
Radiation was delivered to the target tissue with a few millimeters (e.g.,
about
5 mm - 1 cm) standoff between the distal end of the fiber and the target
tissue. The
supraglottis was removed with just one pause to cauterize any incised blood
vessels or
2o to suction any blood away from the target area. Minimal bleeding was
observed, with
blood from incised vessels coagulating as it was exposed to the output from
the fiber.
The procedure lasted about 45 minutes, during which time the supraglottis and
left
cord were removed from the dog.
ADDITIONAL EMBODIMENTS
25 A number of embodiments of the invention have been described.
Nevertheless, it will be understood that various modifications may be made
without
departing from the spirit and scope of the invention. Accordingly, other
embodiments
are within the scope of the following claims.
